This is an automated list of black hole papers, thanks to the arxiv api. (Black holes, hands down, is my favorite cosmic topic.)
I confess that automation is my way of embracing a bit of laziness. When I finish a book I’m left with the dilemma of what to read next, this would then be a great way to face this issue.
pip install arxiv
The list of papers is available in this README.md
But you could access it from this website
| Title | Author(s) | Date | Abstract |
| :—- | :——-: | :–: | ——-: |
| Exact Black String Solutions in Three Dimensions | James H. Horne, Gary T. Horowitz | 1991-08-14 | A family of exact conformal field theories is constructed which describe charged black strings in three dimensions. Unlike previous charged black hole or extended black hole solutions in string theory, the low energy spacetime metric has a regular inner horizon (in addition to the event horizon) and a timelike singularity. As the charge to mass ratio approaches unity, the event horizon remains but the singularity disappears. |
| String Winding in a Black Hole Geometry | Mordechai Spiegelglas | 1991-08-21 | $U(1)$ zero modes in the $SL(2,R)k/U(1)$ and $SU(2)_k/U(1)$ conformal coset theories, are investigated in conjunction with the string black hole solution. The angular variable in the Euclidean version, is found to have a double set of winding. Region III is shown to be $SU(2)_k/U(1)$ where the doubling accounts for the cut sructure of the parafermionic amplitudes and fits nicely across the horizon and singularity. The implications for string thermodynamics and identical particles correlations are discussed. |
| On the Perturbations of String-Theoretic Black Holes | Gerald Gilbert | 1991-08-22 | The perturbations of string-theoretic black holes are analyzed by generalizing the method of Chandrasekhar. Attention is focussed on the case of the recently considered charged string-theoretic black hole solutions as a representative example. It is shown that string-intrinsic effects greatly alter the perturbed motions of the string-theoretic black holes as compared to the perturbed motions of black hole solutions of the field equations of general relativity, the consequences of which bear on the questions of the scattering behavior and the stability of string-theoretic black holes. The explicit forms of the axial potential barriers surrounding the string-theoretic black hole are derived. It is demonstrated that one of these, for sufficiently negative values of the asymptotic value of the dilaton field, will inevitably become negative in turn, in marked contrast to the potentials surrounding the static black holes of general relativity. Such potentials may in principle be used in some cases to obtain approximate constraints on the value of the string coupling constant. The application of the perturbation analysis to the case of two-dimensional string-theoretic black holes is discussed. |
| Superstring Compactification and Target Space Duality | John H. Schwarz | 1991-08-26 | This review talk focusses on some of the interesting developments in the area of superstring compactification that have occurred in the last couple of years. These include the discovery that mirror symmetric" pairs of Calabi--Yau spaces, with completely distinct geometries and topologies, correspond to a single (2,2) conformal field theory. Also, the concept of target-space duality, originally discovered for toroidal compactification, is being extended to Calabi--Yau spaces. It also associates sets of geometrically distinct manifolds to a single conformal field theory. A couple of other topics are presented very briefly. One concerns conceptual challenges in reconciling gravity and quantum mechanics. It is suggested that certaindistasteful allegations” associated with quantum gravity such as loss of quantum coherence, unpredictability of fundamental parameters of particle physics, and paradoxical features of black holes are likely to be circumvented by string theory. Finally there is a brief discussion of the importance of supersymmetry at the TeV scale, both from a practical point of view and as a potentially significant prediction of string theory. |
| Superstring in Two Dimensional Black Hole | Shin’ichi Nojiri | 1991-08-29 | We construct superstring theory in two dimensional black hole background based on supersymmetric $SU(1,1)/U(1)$ gauged Wess-Zumino-Witten model. |
| Effective Superstrings | Zhu Yang | 1991-09-05 | We generalize the method of quantizing effective strings proposed by Polchinski and Strominger to superstrings. The Ramond-Neveu-Schwarz string is different from the Green-Schwarz string in non-critical dimensions. Both are anomaly-free and Poincare invariant. Some implications of the results are discussed. The formal analogy with 4D (super)gravity is pointed out. |
| Some Applications of String Field Theory | Ashoke Sen | 1991-09-12 | We study general properties of the classical solutions in non-polynomial closed string field theory and their relationship with two dimensional conformal field theories. In particular we discuss how different conformal field theories which are related by marginal or nearly marginal deformations can be regarded as different classical solutions of some underlying string field theory. We also discuss construction of a classical solution labelled by infinite number of parameters in string field theory in two dimensions. For a specific set of values of the parameters the solution can be identified to the black hole solution. |
| String Effective Action and Two Dimensional Charged Black Hole | S. Pratik Khastgir, Alok Kumar | 1991-09-14 | Graviton-dilaton background field equations in three space-time dimensions, following from the string effective action are solved when the metric has only time dependence. By taking one of the two space dimensions as compact, our solution reproduces a recently discovered charged black hole solution in two space-time dimensions. Solutions in presence of nonvanishing three dimensional background antisymmetric tensor field are also discussed. |
| On the connection between Quantum Mechanics and the geometry of two-dimensional strings | J. Ellis, N. E. Mavromatos, D. V. Nanopoulos | 1991-09-17 | On the basis of an area-preserving symmetry in the phase space of a one-dimensional matrix model - believed to describe two-dimensional string theory in a black-hole background which also allows for space-time foam - we give a geometric interpretation of the fact that two-dimensional stringy black holes are consistent with conventional quantum mechanics due to the infinite gauged W-hair' property that characterises them. |
| [Beyond the Large N Limit: Non-linear W(infinity) as symmetry of the SL(2,R)/U(1) coset model](http://arxiv.org/abs/hep-th/9109029v1) | I. Bakas, E. Kiritsis | 1991-09-18 | We show that the symmetry algebra of the $SL(2,R)_{k}/U(1)$ coset model is a non-linear deformation of $W_{\infty}$, characterized by $k$. This is a universal $W$-algebra which linearizes in the large $k$ limit and truncates to $W_{N}$ for $k=-N$. Using the theory of non-compact parafermions we construct a free field realization of the non-linear $W_{\infty}$ in terms of two bosons with background charge. The $W$-characters of all unitary $SL(2,R)/U(1)$ representations are computed. Applications to the physics of 2-d black hole backgrounds are also discussed and connections with the KP approach to $c=1$ string theory are outlined. |
| [Elements of String Cosmology](http://arxiv.org/abs/hep-th/9109048v1) | A. A. Tseytlin, C. Vafa | 1991-09-25 | Aspects of string cosmology for critical and non-critical strings are discussed emphasizing the necessity to account for the dilaton dynamics for a proper incorporation of large - small" duality. This drastically modifies the intuition one has with Einstein's gravity. For example winding modes, even though contribute to energy density, oppose expansion and if not annihilated will stop the expansion. Moreover we find that the radiation dominated era of the standard cosmology emerges quite naturally in string cosmology. Our analysis of non-critical string cosmology provides a reinterpretation of the (universal cover of the) recently studied two dimensional black hole solution as a conformal realization of cosmological solutions found previously by Mueller. |
| [Manifestly $O(d,d)$ Invariant Approach to Space-Time Dependent String Vacua](http://arxiv.org/abs/hep-th/9110004v1) | K. A. Meissner, G. Veneziano | 1991-10-01 | An $O(d,d)$ symmetry of the manifold of string vacua that do not depend on $d$ (out of $D$) space-time coordinates has been recently identified. Here we write down, for $d=D-1$, the low energy equations of motion and their general solution in a manifestly $O(d,d)$-invariant form, pointing out an amusing similarity with the renormalization group framework. Previously considered cosmological and black hole solutions are recovered as particular examples. |
| [Open String Theory in 1+1 Dimensions](http://arxiv.org/abs/hep-th/9110034v1) | M. Bershadsky, D. Kutasov | 1991-10-14 | We show that tree level open two dimensional string theory is exactly solvable; the solution exhibits some unusual features, and is qualitatively different from the closed case. The open string tachyon'' S -- matrix describes free fermions, which can be interpreted as the quarks at the ends of the string. These quarks'' live naturally on a lattice in space-time. We also find an exact vacuum solution of the theory, corresponding to a charged black hole. |
| [Superspace WZW Models and Black Holes](http://arxiv.org/abs/hep-th/9110035v1) | Changhyun Ahn, Martin Rocek, Kareljan Schoutens, Alexander Sevrin | 1991-10-14 | We show how to write an off-shell action for the $SU(2)\times U(1)$ supersymmetric WZW model in terms of $N=2$ chiral and twisted chiral multiplets. We discuss the $N=4$ supersymmetry of this model and exhibit the $N=4$ superconformal current algebra. Finally, we show that the off-shell formulation makes it possible to perform a duality transformation, which leads to a supersymmetric sigma model on a manifold with a black hole type singularity. |
| [(Super-) String in Two Dimensional Black Hole and Target Space Dualities](http://arxiv.org/abs/hep-th/9110044v2) | Shin'ichi Nojiri | 1991-10-17 | We review the recently proposed string theory in two dimensional black hole background. Especially, the structure of the duality in the target space is discussed. The duality is analogous to \lq\lq $R \rightarrow 1/R$" symmetry of a compactified boson. We consider the duality in more general target space manifolds which have Killing symmetries and we give an explicit formula which connects two different manifolds which are dual to each other. Superstring theory in two dimensional black hole background is also discussed based on supersymmetric $SU(1,1)/U(1)$ gauged Wess-Zumino-Witten model. |
| [Generalized Duality and Singular Strings in Higher Dimensions](http://arxiv.org/abs/hep-th/9110054v2) | I. Bars, K. Sfetsos | 1991-10-18 | Deformations of gauged WZW actions are constructed for any pair $(G,H)$ by taking different embeddings of the gauge group $H\subset G$ as it acts on the left and right of the group element $g$. This leads to models that are dual to each other, generalizing the axial/vector duality of the two dimensional black hole manifold. The classical equations are completely solved for any pair $(G,H)$ and in particular for the anti de Sitter string based on $SO(d- 1,2)/SO(d-1,1)$ for which the normal modes are determined. Duality is demonstrated for models that have the same set of normal modes. Concentrating on $SO(2,2)/SO(2,1)$, the metric and dilaton fields of the $d=3$ string as well as some of the dual generalizations are obtained. They have curvature singularities and represent new singular solutions of Einstein's general relativity in three dimensions. |
| [Some Exact Solutions of String Theory in Four and Five Dimensions](http://arxiv.org/abs/hep-th/9110067v1) | Petr Horava | 1991-10-24 | We find several classes of exact classical solutions of critical bosonic string theory, constructed as twisted products of one Euclidean and one Minkowskian 2D black hole coset. One class of these solutions leads (after tensoring with free scalars and supersymmetrizing) to a rotating version of the recently discovered exact black fivebrane. Another class represents a one-parameter family of axisymmetric stationary four-dimensional targets with horizons. Global properties and target duality of the 4D solutions are briefly analyzed. |
| [Non-Compact WZW Conformal Field Theories](http://arxiv.org/abs/hep-th/9110076v1) | Krzysztof Gawedzki | 1991-10-31 | We discuss non-compact WZW sigma models, especially the ones with symmetric space $H^{\bf C}/H$ as the target, for $H$ a compact Lie group. They offer examples of non-rational conformal field theories. We remind their relation to the compact WZW models but stress their distinctive features like the continuous spectrum of conformal weights, diverging partition functions and the presence of two types of operators analogous to the local and non-local insertions recently discussed in the Liouville theory. Gauging non-compact abelian subgroups of $H^{\bf C}$ leads to non-rational coset theories. In particular, gauging one-parameter boosts in the $SL(2,\bC)/SU(2)$ model gives an alternative, explicitly stable construction of a conformal sigma model with the euclidean 2D black hole target. We compute the (regularized) toroidal partition function and discuss the spectrum of the theory. A comparison is made with more standard approach based on the $U(1)$ coset of the $SU(1,1)$ WZW theory where stability is not evident but where unitarity becomes more transparent. |
| [Topological Field Theories and Space-Time Singularity](http://arxiv.org/abs/hep-th/9111001v1) | Tohru Eguchi | 1991-11-01 | Based on a study of recently proposed solution of 2 dim. black hole we argue that the space-time singularities of general relativity may be described by topological field theories (TFTs). We also argue that in general TFT is a field theory which decsribes singular configurations with a reduced holonomy in its field space. |
| [On the Evaporation of Black Holes in String Theory](http://arxiv.org/abs/hep-th/9111031v1) | J. Ellis, N. E. Mavromatos, D. V. Nanopoulos | 1991-11-18 | We show that, in string theory, the quantum evaporation and decay of black holes in two-dimensional target space is related to imaginary parts in higher-genus string amplitudes. These arise from the regularisation of modular infinities due to the sum over world-sheet configurations, that are known to express the instabilities of massive string states in general, and are not thermal in character. The absence of such imaginary parts in the matrix model limit confirms that the latter constitutes the final stage of the evaporation process, at least in perturbation theory. Our arguments appear to be quite generic, related only to the summation over world-sheet surfaces, and hence should also apply to higher-dimensional target spaces. |
| [Charged Black Holes in Two-Dimensional String Theory](http://arxiv.org/abs/hep-th/9111038v1) | Michael D. McGuigan, Chiara R. Nappi, Scott A. Yost | 1991-11-20 | We discuss two dimensional string theories containing gauge fields introduced either via coupling to open strings, in which case we get a Born-Infeld type action, or via heterotic compactification. The solutions to the modified background field equations are charged black holes which exhibit interesting space-time geometries. We also compute their masses and charges. |
| [Instabilities in the gravitational background and string theory](http://arxiv.org/abs/hep-th/9111041v1) | Anirvan M. Sengupta | 1991-11-21 | We indicate the tentative source of instability in the two-dimensional black hole background. There are relevant operators among the tachyon and the higher level vertex operators in the conformal field theory. Connection of this instability with Hawking radiation is not obvious. The situation is somewhat analogous to fields in the background of a negative mass Euclidean Schwarzschild solution (in four dimensions). Speculation is made about decay of the Minkowski black hole into finite temperature flat space. |
| ["the Instability of String-Theoretic Black Holes"](http://arxiv.org/abs/hep-th/9111042v1) | Gerald Gilbert | 1991-11-21 | It is demonstrated that static, charged, spherically--symmetric black holes in string theory are classically and catastrophically unstable to linearized perturbations in four dimensions, and moreover that unstable modes appear for arbitrarily small positive values of the charge. This catastrophic classical instability dominates and is distinct from much smaller and less significant effects such as possible quantum mechanical evaporation. The classical instability of the string--theoretic black hole contrasts sharply with the situation which obtains for the Reissner--Nordstr\"om black hole of general relativity, which has been shown by Chandrasekhar to be perfectly stable to linearized perturbations at the event horizon. |
| [Modified Black Holes in Two Dimensional Gravity](http://arxiv.org/abs/hep-th/9111044v1) | N. Mohammedi | 1991-11-22 | The $SL(2,R)/U(1)$ gauged WZWN model is modified by a topological term and the accompanying change in the geometry of the two dimensional target space is determined. The possibility of this additional term arises from a symmetry in the general formalism of gauging an isometry subgroup of a non-linear sigma model with an antisymmetric tensor. It is shown, in particular, that the space-time exhibits some general singularities for which the recently found black hole is just a special case. From a conformal field theory point of view and for special values of the unitary representations of $SL(2,R)$, this topological term can be interpreted as a small perturbation by a (1,1) conformal operator of the gauged WZWN action. |
| [A Classical Instability of Reissner-Nordstrom Solutions and the Fate of Magnetically Charged Black Holes](http://arxiv.org/abs/hep-th/9111045v2) | K. Lee, V. P. Nair, E. J. Weinberg | 1991-11-22 | Working in the context of spontaneously broken gauge theories, we show that the magnetically charged Reissner-Nordstrom solution develops a classical instability if the horizon is sufficiently small. This instability has significant implications for the evolution of a magnetically charged black hole. In particular, it leads to the possibility that such a hole could evaporate completely, leaving in its place a nonsingular magnetic monopole. |
| [On Black Holes In String Theory](http://arxiv.org/abs/hep-th/9111052v1) | Edward Witten | 1991-11-25 | In these lecture notes from Strings 91, I briefly sketch the analogy between two dimensional black holes and the s-wave sector of four dimensional black holes, and the physical interest of the latter, particularly in the magnetically charged case. |
| Evanescent Black Holes | C. Callan, S. Giddings, J. Harvey, A. Strominger | 1991-11-28 | A renormalizable theory of quantum gravity coupled to a dilaton and conformal matter in two space-time dimensions is analyzed. The theory is shown to be exactly solvable classically. Included among the exact classical solutions are configurations describing the formation of a black hole by collapsing matter. The problem of Hawking radiation and backreaction of the metric is analyzed to leading order in a $1/N$ expansion, where $N$ is the number of matter fields. The results suggest that the collapsing matter radiates away all of its energy before an event horizon has a chance to form, and black holes thereby disappear from the quantum mechanical spectrum. It is argued that the matter asymptotically approaches a zero-energy bound state'' which can carry global quantum numbers and that a unitary $S$-matrix including such states should exist. |
| [Perturbations of a Stringy Black Hole](http://arxiv.org/abs/hep-th/9112001v2) | E. Raiten | 1991-12-02 | We extend the three dimensional stringy black hole of Horne and Horowitz to four dimensions. After a brief discussion of the global properties of the metric, we discuss the stability of the background with respect to small perturbations, following the methods of Gilbert and of Chandrasekhar. The potential for axial perturbations is found to be positive definite. |
| [Black Holes in Magnetic Monopoles](http://arxiv.org/abs/hep-th/9112008v1) | K. Lee, V. P. Nair, Erick J. Weinberg | 1991-12-04 | We study magnetically charged classical solutions of a spontaneously broken gauge theory interacting with gravity. We show that nonsingular monopole solutions exist only if the Higgs vacuum expectation value $v$ is less than or equal to a critical value $v_{cr}$, which is of the order of the Planck mass. In the limiting case the monopole becomes a black hole, with the region outside the horizon described by the critical Reissner-Nordstrom solution. For $v<v_{cr}$, we find additional solutions which are singular at $r=0$, but which have this singularity hidden within a horizon. These have nontrivial matter fields outside the horizon, and may be interpreted as small black holes lying within a magnetic monopole. The nature of these solutions as a function of $v$ and of the total mass $M$ and their relation to the Reissner-Nordstrom solutions is discussed. |
| [Nonlinear $\hat{W}_{\infty}$ Current Algebra in the SL(2,R)/U(1) Coset Model](http://arxiv.org/abs/hep-th/9112009v1) | Feng Yu, Yong-Shi Wu | 1991-12-04 | Previously we have established that the second Hamiltonian structure of the KP hierarchy is a nonlinear deformation, called $\hat{W}_{\infty}$, of the linear, centerless $W_{\infty}$ algebra. In this letter we present a free-field realization for all generators of $\hat{W}_{\infty}$ in terms of two scalars as well as an elegant generating function for the $\hat{W}_{\infty}$ currents in the classical conformal $SL(2,R)/U(1)$ coset model. After quantization, a quantum deformation of $\hat{W}_{\infty}$ appears as the hidden current algebra in this model. The $\hat{W}_{\infty}$ current algebra results in an infinite set of commuting conserved charges, which might give rise to $W$-hair for the 2d black hole arising in the corresponding string theory at level $k=9/4$. |
| [Quantum Mechanics and Black Holes in Four-Dimensional String Theory](http://arxiv.org/abs/hep-th/9112062v1) | J. Ellis, N. Mavromatos, D. Nanopoulos | 1991-12-20 | In previous papers we have shown how strings in a two-dimensional target space reconcile quantum mechanics with general relativity, thanks to an infinite set of conserved quantum numbers,W-hair’’, associated with topological soliton-like states. In this paper we extend these arguments to four dimensions, by considering explicitly the case of string black holes with radial symmetry. The key infinite-dimensional W-symmetry is associated with the $\frac{SU(1,1)}{U(1)}$ coset structure of the dilaton-graviton sector that is a model-independent feature of spherically symmetric four-dimensional strings. Arguments are also given that the enormous number of string {\it discrete (topological)} states account for the maintenance of quantum coherence during the (non-thermal) stringy evaporation process, as well as quenching the large Hawking-Bekenstein entropy associated with the black hole. Defining the latter as the measure of the loss of information for an observer at infinity, who - ignoring the higher string quantum numbers - keeps track only of the classical mass,angular momentum and charge of the black hole, one recovers the familiar a quadratic dependence on the black-hole mass by simple counting arguments on the asymptotic density of string states in a linear-dilaton background. |
| Euclidean Black Hole Vortices | Fay Dowker, Ruth Gregory, Jennie Traschen | 1991-12-20 | We argue the existence of solutions of the Euclidean Einstein equations that correspond to a vortex sitting at the horizon of a black hole. We find the asymptotic behaviours, at the horizon and at infinity, of vortex solutions for the gauge and scalar fields in an abelian Higgs model on a Euclidean Schwarzschild background and interpolate between them by integrating the equations numerically. Calculating the backreaction shows that the effect of the vortex is to cut a slice out of the Euclidean Schwarzschild geometry. Consequences of these solutions for black hole thermodynamics are discussed. |
| Generalized Duality in Curved String-Backgrounds | Amit Giveon, Martin Rocek | 1991-12-23 | The elements of $O(d,d,\Z)$ are shown to be discrete symmetries of the space of curved string backgrounds that are independent of $d$ coordinates. The explicit action of the symmetries on the backgrounds is described. Particular attention is paid to the dilaton transformation. Such symmetries identify different cosmological solutions and other (possibly) singular backgrounds; for example, it is shown that a compact black string is dual to a charged black hole. The extension to the heterotic string is discussed. |
| Factorizations of natural embeddings of l_p^n int L_r | Tadek Figiel, William B. Johnson, Gideon Schechtman | 1992-01-06 | This is a continuation of the paper [FJS] with a similar title. Several results from there are strengthened, in particular: 1. If T is a “natural” embedding of l_2^n into L_1 then, for any well-bounded factorization of T through an L_1 space in the form T=uv with v of norm one, u well-preserves a copy of l_1^k with k exponential in n. 2. Any norm one operator from a C(K) space which well-preserves a copy of l_2^n also well-preserves a copy of l{\infty}^k with k exponential in n. As an application of these and other results we show the existence, for any n, of an n-dimensional space which well-embeds into a space with an unconditional basis only if the latter contains a copy of l_{\infty}^k with k exponential in n. |
| An Algorithm to Generate Classical Solutions for String Effective Action | S. Kar, S. Khastgir, A. Kumar | 1992-01-07 | It is shown explicitly, that a number of solutions for the background field equations of the string effective action in space-time dimension D can be generated from any known lower dimensional solution, when background fields have only time dependence. An application of the result to the two dimensional charged black hole is presented. The case of background with more general coordinate dependence is also discussed. |
| A Note on Background (In)dependence | Nathan Seiberg, Stephen Shenker | 1992-01-09 | In general quantum systems there are two kinds of spacetime modes, those that fluctuate and those that do not. Fluctuating modes have normalizable wavefunctions. In the context of 2D gravity and non-critical'' string theory these are called macroscopic states. The theory is independent of the initial Euclidean background values of these modes. Non-fluctuating modes have non-normalizable wavefunctions and correspond to microscopic states. The theory depends on the background value of these non-fluctuating modes, at least to all orders in perturbation theory. They are superselection parameters and should not be minimized over. Such superselection parameters are well known in field theory. Examples in string theory include the couplings $t_k$ (including the cosmological constant) in the matrix models and the mass of the two-dimensional Euclidean black hole. We use our analysis to argue for the finiteness of the string perturbation expansion around these backgrounds. |
| [Scalar-Tensor Quantum Gravity in Two Dimensions](http://arxiv.org/abs/hep-th/9201021v2) | J. Russo, A. A. Tseytlin | 1992-01-12 | We discuss some classical and quantum properties of 2d gravity models involving metric and a scalar field. Different models are parametrized in terms of a scalar potential. We show that a general Liouville-type model with exponential potential and linear curvature coupling is renormalisable at the quantum level while a particular model (corresponding to D=2 graviton-dilaton string effective action and having a black hole solution) is finite. We use the condition of asplit” Weyl symmetry to suggest possible expressions for the effective" action which includes the quantum anomaly term. |
| [Supersymmetric Black Holes](http://arxiv.org/abs/hep-th/9201029v1) | Renata Kallosh | 1992-01-15 | The effective action of $N=2$, $d=4$ supergravity is shown to acquire no quantum corrections in background metrics admitting super-covariantly constant spinors. In particular, these metrics include the Robinson-Bertotti metric (product of two 2-dimensional spaces of constant curvature) with all 8 supersymmetries unbroken. Another example is a set of arbitrary number of extreme Reissner-Nordstr\"om black holes. These black holes break 4 of 8 supersymmetries, leaving the other 4 unbroken. We have found manifestly supersymmetric black holes, which are non-trivial solutions of the flatness condition $\cd^{2} = 0$ of the corresponding (shortened) superspace. Their bosonic part describes a set of extreme Reissner-Nordstr\"om black holes. The super black hole solutions are exact even when all quantum supergravity corrections are taken into account. |
| [Exact Bosonic and Supersymmetric String Black Hole Solutions](http://arxiv.org/abs/hep-th/9201039v1) | I. Jack, D. R. T. Jones, J. Panvel | 1992-01-21 | We show that Witten's two-dimensional string black hole metric is exactly conformally invariant in the supersymmetric case. We also demonstrate that this metric, together with a recently proposed exact metric for the bosonic case, are respectively consistent with the supersymmetric and bosonic $\sigma$-model conformal invariance conditions up to four-loop order. |
| [Quantum Hair on Black Holes](http://arxiv.org/abs/hep-th/9201059v1) | Sidney Coleman, John Preskill, Frank Wilczek | 1992-01-28 | A black hole may carry quantum numbers that are {\it not} associated with massless gauge fields, contrary to the spirit of theno-hair’’ theorems. We describe in detail two different types of black hole hair that decay exponentially at long range. The first type is associated with discrete gauge charge and the screening is due to the Higgs mechanism. The second type is associated with color magnetic charge, and the screening is due to color confinement. In both cases, we perform semi-classical calculations of the effect of the hair on local observables outside the horizon, and on black hole thermodynamics. These effects are generated by virtual cosmic strings, or virtual electric flux tubes, that sweep around the event horizon. The effects of discrete gauge charge are non-perturbative in $\hbar$, but the effects of color magnetic charge become $\hbar$-independent in a suitable limit. We present an alternative treatment of discrete gauge charge using dual variables, and examine the possibility of black hole hair associated with discrete {\it global} symmetry. We draw the distinction between {\it primary} hair, which endows a black hole with new quantum numbers, and {\it secondary} hair, which does not, and we point out some varieties of secondary hair that occur in the standard model of particle physics. |
| Are Horned Particles the Climax of Hawking Evaporation? | T. Banks, A. Dabolkhar, M. R. Douglas, M. O’ Loughlin | 1992-01-28 | We investigate the proposal by Callan, Giddings, Harvey and Strominger (CGHS) that two dimensional quantum fluctuations can eliminate the singularities and horizons formed by matter collapsing on the nonsingular extremal black hole of dilaton gravity. We argue that this scenario could in principle resolve all of the paradoxes connected with Hawking evaporation of black holes. However, we show that the generic solution of the model of CGHS is singular. We propose modifications of their model which may allow the scenario to be realized in a consistent manner. |
| On the Black-Hole Conformal Field Theory Coupled to the Polyakov’s String Theory. A Non Perturbative Analysis | M. Martellini, M. Spreafico, K. Yoshida | 1992-01-29 | We couple the 2D black-hole conformal field theory discovered by Witten to a $D-1$ dimensional Euclidean bosonic string. We demonstrate that the resulting planar (=zero genus) string susceptibility is real for any $0\leq D \leq 4$. |
| Black Hole Evaporation in 1+1 Dimensions | J. Russo, L. Susskind, L. Thorlacius | 1992-01-29 | The formation and quantum mechanical evaporation of black holes in two spacetime dimensions can be studied using effective classical field equations, recently introduced by Callan {\it et al.} We find that gravitational collapse always leads to a curvature singularity, according to these equations, and that the region where the quantum corrections introduced by Callan {\it et al.} could be expected to dominate is on the unphysical side of the singularity. The model can be successfully applied to study the back-reaction of Hawking radiation on the geometry of large mass black holes, but the description breaks down before the evaporation is complete. |
| Dynamics of Extremal Black Holes | S. B. Giddings, A. Strominger | 1992-02-03 | Particle scattering and radiation by a magnetically charged, dilatonic black hole is investigated near the extremal limit at which the mass is a constant times the charge. Near this limit a neighborhood of the horizon of the black hole is closely approximated by a trivial product of a two-dimensional black hole with a sphere. This is shown to imply that the scattering of long-wavelength particles can be described by a (previously analyzed) two-dimensional effective field theory, and is related to the formation/evaporation of two-dimensional black holes. The scattering proceeds via particle capture followed by Hawking re-emission, and naively appears to violate unitarity. However this conclusion can be altered when the effects of backreaction are included. Particle-hole scattering is discussed in the light of a recent analysis of the two-dimensional backreaction problem. It is argued that the quantum mechanical possibility of scattering off of extremal black holes implies the potential existence of additional quantum numbers - referred to as quantum whiskers'' - characterizing the black hole. |
| [Exact Solutions of Four Dimensional Black Holes in String Theory](http://arxiv.org/abs/hep-th/9202005v1) | David Gershon | 1992-02-03 | We construct an exact CFT as an SL(2,R)xSU(2)/U(1)^2 gauged WZW model, which describes a black hole in 4 dimensions. Another exact solution, describing a black membrane in 4D (in the sense that the event horizon is an infinite plane) is found as an SL(2,R)xU(1)^2/U(1) gauged WZW model. Finally, we construct an exact solution of a 4D black hole with electromagnetic field, as an SL(2,R)xSU(2)xU(1)/U(1)^2 gauged WZW model. This black hole carries both electric and axionic charges. |
| [Black Holes as Elementary Particles](http://arxiv.org/abs/hep-th/9202014v1) | C. F. E. Holzhey, F. Wilczek | 1992-02-05 | It is argued that the qualitative features of black holes, regarded as quantum mechanical objects, depend both on the parameters of the hole and on the microscopic theory in which it is embedded. A thermal description is inadequate for extremal holes. In particular, extreme holes of the charged dilaton family can have zero entropy but non-zero, and even (for $a>1$) formally infinite, temperature. The existence of a tendency to radiate at the extreme, which threatens to overthrow any attempt to identify the entropy as available internal states and also to expose a naked singularity, is at first sight quite disturbing. However by analyzing the perturbations around the extreme holes we show that these holes are protected by mass gaps, or alternatively potential barriers, which remove them from thermal contact with the external world. We suggest that the behavior of these extreme dilaton black holes, which from the point of view of traditional black hole theory seems quite bizarre, can reasonably be interpreted as the holes doing their best to behave like normal elementary particles. The $a<1$ holes behave qualitatively as extended objects. |
| [Spinning Braid Group Representation and the Fractional Quantum Hall
Effect](http://arxiv.org/abs/hep-th/9202024v1) | Christopher Ting, C. H. Lai | 1992-02-07 | The path integral approach to representing braid group is generalized for particles with spin. Introducing the notion of {\em charged} winding number in the super-plane, we represent the braid group generators as homotopically constrained Feynman kernels. In this framework, super Knizhnik-Zamolodchikov operators appear naturally in the Hamiltonian, suggesting the possibility of {\em spinning nonabelian} anyons. We then apply our formulation to the study of fractional quantum Hall effect (FQHE). A systematic discussion of the ground states and their quasi-hole excitations is given. We obtain Laughlin, Halperin and Moore-Read states as {\em exact} ground state solutions to the respective Hamiltonians associated to the braid group representations. The energy gap of the quasi-excitation is also obtainable from this approach. |
| [Black Holes in Higher Derivative Gravity Theories](http://arxiv.org/abs/hep-th/9202031v2) | S. Mignemi, D. L. Wiltshire | 1992-02-08 | We study static spherically symmetric solutions of Einstein gravity plus an action polynomial in the Ricci scalar, $R$, of arbitrary degree, $n$, in arbitrary dimension, $D$. The global properties of all such solutions are derived by studying the phase space of field equations in the equivalent theory of gravity coupled to a scalar field, which is obtained by a field redefinition and conformal transformation. The following uniqueness theorem is obtained: provided that the coefficient of the $R^2$ term in the Lagrangian polynomial is positive then the only static spherically symmetric asymptotically flat solution with a regular horizon in these models is the Schwarzschild solution. Other branches of solutions with regular horizons, which are asymptotically anti-de Sitter, or de Sitter, are also found. An exact Schwarzschild-de Sitter type solution is found to exist in the $R+aR^2$ if $D>4$. If terms of cubic or higher order in $R$ are included in the action, then such solutions also exist in four dimensions. The general Schwarzschild-de Sitter type solution for arbitrary $D$ and $n$ is given. The fact that the Schwarzschild solution in these models does not coincide with the exterior solution of physical bodies such as stars has important physical implications which we discuss. As a byproduct, we classify all static spherically symmetric solutions of $D$-dimensional gravity coupled to a scalar field with a potential consisting of a finite sum of exponential terms. |
| [Splitting of an Extremal Reissner-Nordström Throat via Quantum
Tunneling](http://arxiv.org/abs/hep-th/9202037v2) | Dieter R. Brill | 1992-02-12 | The interior near the horizon of an extremal Reissner-Nordstr\"om black hole is taken as an initial state for quantum mechanical tunneling. An instanton is presented that connects this state with a final state describing the presence of several horizons. This is interpreted as a WKB description of fluctuations due to the throat splitting into several components. |
| [An Alternative Scenario for Non-Abelian Quantum Hair](http://arxiv.org/abs/hep-th/9202045v1) | Amitabha Lahiri | 1992-02-13 | Topologically charged black holes in a theory with a 2-form coupled to a non-abelian gauge field are investigated. It is found that the classification of the ground states is similar to that in the theory of non-abelian discrete quantum hair. |
| [Properties of Asymptotically Flat Two-Dimensional Black Holes](http://arxiv.org/abs/hep-th/9202068v1) | R. B. Mann, M. S. Morris, S. F. Ross | 1992-02-19 | We investigate properties of two-dimensional asymptotically flat black holes which arise in both string theory and in scale invariant theories of gravity. By introducing matter sources in the field equations we show how such objects can arise as the endpoint of gravitational collapse. We examine the motion of test particles outside the horizons, and show that they fall through in a finite amount of proper time and an infinite amount of coordinate time. We also investigate the thermodynamic and quantum properties, which give rise to a fundamental length scale. The 't Hooft prescription for cutting off eigenmodes of particle wave functions is shown to be source dependent, unlike the four-dimensional case. The relationship between these black holes and those considered previously in $(1+1)$ dimensions is discussed. |
| [S-Wave Scattering of Charged Fermions by a Magnetic Black Hole](http://arxiv.org/abs/hep-th/9202075v1) | Mark Alford, Andrew Strominger | 1992-02-21 | We argue that, classically, $s$-wave electrons incident on a magnetically charged black hole are swallowed with probability one: the reflection coefficient vanishes. However, quantum effects can lead to both electromagnetic and gravitational backscattering. We show that, for the case of extremal, magnetically charged, dilatonic black holes and a single flavor of low-energy charged particles, this backscattering is described by a perturbatively computable and unitary $S$-matrix, and that the Hawking radiation in these modes is suppressed near extremality. The interesting and much more difficult case of several flavors is also discussed. |
| [A Possible Black Hole Background in c=1 Matrix Model](http://arxiv.org/abs/hep-th/9202078v2) | Zhu Yang | 1992-02-22 | We propose a new space-time interpretation for c=1 matrix model with potential $V(x)=-x^{2}/2-\m^{2}/2x^{2}$. It is argued that this particular potential corresponds to a black hole background. Some related issues are discussed. |
| [Strings on Curved Spacetimes: Black Holes, Torsion, and Duality](http://arxiv.org/abs/hep-th/9202092v1) | Paul Ginsparg, Fernando Quevedo | 1992-02-29 | We present a general discussion of strings propagating on noncompact coset spaces $G/H$ in terms of gauged WZW models, emphasizing the role played by isometries in the existence of target space duality. Fixed points of the gauged transformations induce metric singularities and, in the case of abelian subgroups $H$, become horizons in a dual geometry. We also give a classification of models with a single timelike coordinate together with an explicit list for dimensions $D\leq 10$. We study in detail the class of models described by the cosets $SL(2,\IR)\otimes SO(1,1)^{D-2}/SO(1,1)$. For $D\geq 2$ each coset represents two different spacetime geometries: (2D black hole)$\otimes \IR^{D-2}$ and (3D black string)$\otimes \IR^{D-3}$ with nonvanishing torsion. They are shown to be dual in such a way that the singularity of the former geometry (which is not due to a fixed point) is mapped to a regular surface (i.e.\ not even a horizon) in the latter . These cosets also lead to the conformal field theory description of known and new cosmological string models. |
| [Measuring the $W$-hair of String Black Holes](http://arxiv.org/abs/hep-th/9203012v1) | John Ellis, N. E. Mavromatos, D. V. Nanopoulos | 1992-03-05 | We have argued previously that the infinitely many gauge symmetries of string theory provide an infinite set of conserved (gauge) quantum numbers ($W$-hair) which characterise black hole states and maintain quantum coherence. Here we study ways of measuring the $W$-hair of spherically-symmetric four-dimensional objects with event horizons, treated as effectively two-dimensional string black holes. Measurements can be done either through the s-wave scattering of light particles off the string black-hole background, or through interference experiments of Aharonov-Bohm type. In the first type of measurement, selection rules |
| [Supersymmetric, cold and lukewarm black holes in cosmological
Einstein-Maxwell theory](http://arxiv.org/abs/hep-th/9203018v1) | L. J. Romans | 1992-03-08 | In flat space, the extreme Reissner-Nordstr\o m (RN) black hole is distinguished by its coldness (vanishing Hawking temperature) and its supersymmetry. We examine RN solutions to Einstein-Maxwell theory with a cosmological constant $\Lambda$, classifying the cold black holes and, for positive $\Lambda$, thelukewarm” black holes at the same temperature as the de Sitter thermal background. For negative $\Lambda$, we classify the supersymmetric solutions within the context of $N=2$ gauged supergravity. One finds supersymmetric analogues of flat-space extreme RN black holes, which for nonzero $\Lambda$ differ from the cold black holes. In addition, there is an exotic class of supersymmetric solutions which cannot be continued to flat space, since the magnetic charge becomes infinite in that limit. |
| Two Dimensional Stringy Black Holes with One Asymptotically Flat Domain | Petr Horava | 1992-03-11 | The exact black hole solution of 2D closed string theory has, as any other maximally extended Schwarzschild-like geometry, two asymptotically flat spacetime domains. One can get rid of the second domain by gauging the discrete symmetry on the SL(2,R)/U(1) coset that interchanges the two asymptotic domains and preserves the Kruskal time orientation everywhere in the Kruskal plane. Here it is shown that upon performing this orbifold procedure, we obtain a theory of unoriented open and closed strings in a black hole background, with just one asymptotically flat domain and a time-like orbifold singularity at the origin. All of the open string states of the model are confined to the orbifold singularity. We also discuss various physical aspects of the truncated black hole, in particular its target duality – the model is dual to a conventional open string theory in the black hole geometry. |
| Black Holes from Non-Abelian Toda Theories | Jean-Loup Gervais, Mikhail V. Saveliev | 1992-03-17 | NON-ABELIAN TODA THEORIES are shown to provide EXACTLY SOLVABLE conformal systems in the presence of a BLACK HOLE which may be regarded as describing a string propagating in target space with a black-hole metric. These theories are associated with non-canonical $\bf Z$-gradations of simple algebras, where the gradation-zero subgroup is non-abelian. They correspond to gauged WZNW models where the gauge group is nilpotent and are thus basically different from the ones currently considered following Witten. The non-abelian Toda potential gives a cosmological term which may be exactly integrated at the classical level. |
| The Causal Structure of Two-Dimensional Spacetimes | Dan Christensen, Robert B. Mann | 1992-03-18 | We investigate the causal structure of $(1+1)$-dimensional spacetimes. For two sets of field equations we show that at least locally any spacetime is a solution for an appropriate choice of the matter fields. For the theories under consideration we investigate how smoothness of their black hole solutions affects time orientation. We show that if an analog to Hawking’s area theorem holds in two spacetime dimensions, it must actually state that the size of a black hole never {\em increases}, contrary to what happens in four dimensions. Finally, we discuss the applicability of the Penrose and Hawking singularity theorems to two spacetime dimensions. |
| Evaporation of Two Dimensional Black Holes | S. W. Hawking | 1992-03-18 | Callan, Giddings, Harvey and Strominger have proposed an interesting two dimensional model theory that allows one to consider black hole evaporation in the semi-classical approximation. They originally hoped the black hole would evaporate completely without a singularity. However, it has been shown that the semi-classical equations will give a singularity where the dilaton field reaches a certain critical value. Initially, it seems this singularity will be hidden inside a black hole. However, as the evaporation proceeds, the dilaton field on the horizon will approach the critical value but the temperature and rate of emission will remain finite. These results indicate either that there is a naked singularity, or (more likely) that the semi-classical approximation breaks down when the dilaton field approaches the critical value. |
| Hawking Radiation and Back-Reaction | L. Susskind, L. Thorlacius | 1992-03-20 | The puzzles of black hole evaporation can be studied in the simplified context of 1+1 dimensional gravity. The semi-classical equations of Callan, Giddings, Harvey and Strominger provide a consistent description of the evaporation process which we describe in detail. We consider the possibility that black hole evolution leads to massive stable remnants. We show that such zero temperature remnant solutions exist but we also prove that a decaying black hole cannot evolve into one of them. Finally we consider the issue of loss of quantum information behind the global event horizon which develops in these geometries. An analogy with a well known solvable system shows that there may be less to information than meets the eye. |
| Black Holes and Massive Remnants | S. B. Giddings | 1992-03-21 | This paper revisits the conundrum faced when one attempts to understand the dynamics of black hole formation and evaporation without abandoning unitary evolution. Previous efforts to resolve this puzzle assume that information escapes in corrections to the Hawking process, that an arbitrarily large amount of information is transmitted by a planckian energy or contained in a Planck-sized remnant, or that the information is lost to another universe. Each of these possibilities has serious difficulties. This paper considers another alternative: remnants that carry large amounts of information and whose size and mass depend on their information content. The existence of such objects is suggested by attempts to incorporate a Planck scale cutoff into physics. They would greatly alter the late stages of the evaporation process. The main drawback of this scenario is apparent acausal behavior behind the horizon. |
| Target Space Structure of a Chiral Gauged Wess-Zumino-Witten Model | Supriya K. Kar, Alok Kumar | 1992-03-27 | The background for string propagation is obtained by a chiral gauging of the $SL(2,R)$ Wess-Zumino-Witten model. It is shown explicitly that the resulting background fields satisfy the field equations of the three dimensional string effective action and the target space has curvature singularity. Close connection of our solution with the three dimensional black string is demonstrated. |
| Rotating Dilaton Black Holes | James H. Horne, Gary T. Horowitz | 1992-03-30 | It is shown that an arbitrarily small amount of angular momentum can qualitatively change the properties of extremal charged black holes coupled to a dilaton. In addition, the gyromagnetic ratio of these black holes is computed and an exact rotating black string solution is presented. |
| Noncompact Coset Spaces in String Theory | Fernando Quevedo | 1992-04-03 | A brief overview of strings propagating on noncompact coset spaces G/H is presented in terms of WZW models. The role played by isometries in the existence of target space duality and by fixed points of the gauge transformations in the existence of singularities and horizons, is emphasized. A general classification of the spaces with a single time-like coordinate is presented. The spacetime geometry of a class of models, existing for every dimension and having cosmological and black hole-like interpretations, is discussed. |
| Dilaton Gravity and No-Hair Theorem in Two Dimensions | Olaf Lechtenfeld, Chiara Nappi | 1992-04-10 | We study a general class of two-dimensional theories of the dilaton-gravity type inspired by string theory and show that they admit charged multiple-horizon black holes. These solutions are proved to satisfy scalar no-hair theorems. |
| Quantum Fermion Hair | Ruth Gregory, Jeffrey Harvey | 1992-04-10 | It is shown that the Dirac operator in the background of a magnetic %Reissner-Nordstr"om black hole and a Euclidean vortex possesses normalizable zero modes in theories containing superconducting cosmic strings. One consequence of these zero modes is the presence of a fermion condensate around magnetically charged black holes which violates global quantum numbers. |
| Gamma-Ray Bursts as the Death Throes of Massive Binary Stars | Ramesh Narayan, Bohdan Paczyński, Tsvi Piran | 1992-04-13 | It is proposed that gamma-ray bursts are created in the mergers of double neutron star binaries and black hole neutron star binaries at cosmological distances. Bursts with complex profiles and relatively long durations are the result of magnetic flares generated by the Parker instability in a post-merger differentially-rotating disk. Some bursts may also be produced through neutrino-antineutrino annihilation into electrons and positrons. In both cases, an optically thick fireball of size $\sles\ 100$ km is initially created, which expands ultrarelativistically to large radii before radiating. Several previous objections to the cosmological merger model are eliminated. It is predicted that $\gamma$-ray bursts will be accompanied by a burst of gravitational radiation from the spiraling-in binary which could be detected by LIGO. |
| On the Stability of a Stringy Black Hole | A. Carlini, F. Fucito, M. Martellini | 1992-04-13 | We study the stability under perturbations of a charged four dimensional stringy black hole arising from gauging a previously studied WZW model. We find that the black hole is stable only in the extremal case $Q=M$. |
| Asymptotic Behavior of 2-d Black Holes | E. Raiten | 1992-04-15 | We consider the solutions of the field equations for the large $N$ dilaton gravity model in $1+1$ dimensions recently proposed by Callan, Giddings, Harvey and Strominger (CGHS). We find time dependant solutions with finite mass and vanishing flux in the weak coupling regime, as well as solutions which lie entirely in the Liouville region. |
| Rotating Charged Black Hole Solution in Heterotic String Theory | Ashoke Sen | 1992-04-15 | We construct a solution of the classical equations of motion arising in the low energy effective field theory for heterotic string theory. This solution describes a black hole in four dimensions carrying mass $M$, charge $Q$ and angular momentum $J$. The extremal limit of the solution is discussed. |
| Hawking radiation: a particle physics perspective | Matt Visser | 1992-04-20 | It has recently become fashionable to regard black holes as elementary particles. By taking this suggestion seriously it is possible to cobble together an elementary particle physics based estimate for the decay rate $(\hbox{black hole})i \to (\hbox{black hole})_f + (\hbox{massless quantum})$. This estimate of the spontaneous emission rate contains two free parameters which may be fixed by demanding that the high energy end of the spectrum of emitted quanta match a blackbody spectrum at the Hawking temperature. The calculation, though technically trivial, has important conceptual implications: (1) The existence of Hawking radiation from black holes is ultimately dependent only on the fact that massless quanta (and all other forms of matter) couple to gravity. (2) The thermal nature of the Hawking spectrum depends only on the fact that the number of internal states of a large mass black hole is enormous. (3) Remarkably, the resulting formula for the decay rate gives meaningful answers even when extrapolated to low mass black holes. The analysis strongly supports the scenario of complete evaporation as the endpoint of the Hawking radiation process (no naked singularity, no stable massive remnant). |
| Quantum Emission from Two-Dimensional Black Holes | Steven B. Giddings, W. M. Nelson | 1992-04-22 | We investigate Hawking radiation from two-dimensional dilatonic black holes using standard quantization techniques. In the background of a collapsing black hole solution the Bogoliubov coefficients can be exactly determined. In the regime after the black hole has settled down to an equilibrium' state but before the backreaction becomes important these give the known result of a thermal distribution of Hawking radiation at temperature lambda/(2pi). The density matrix is computed in this regime and shown to be purely thermal. Similar techniques can be used to derive the stress tensor. The resulting expression agrees with the derivation based on the conformal anomaly and can be used to incorporate the backreaction. Corrections to the thermal density matrix are also examined, and it is argued that to leading order in perturbation theory the effect of the backreaction is to modify the Bogoliubov transformation, but not in a way that restores information lost to the black holes. |
| [The Physics of 2-d Stringy Spacetimes](http://arxiv.org/abs/hep-th/9204090v1) | Gary W. Gibbons, Malcolm J. Perry | 1992-04-28 | We examine the two-dimensional spacetimes that emerge from string theory. We find all the solutions with no tachyons, and show that the only non-trivial solution is the black hole spacetime. We examine the role of duality in this picture. We then explore the thermodynamics of these solutions which is complicated by the fact that only in two spacetime dimensions is it impossible to redefine the dilaton field in terms of a canonical scalar field. Finally, we extend our analysis to the heterotic string, and briefly comment on exact, as opposed to perturbative, solutions. |
| [On the W-hair of String Black Holes and the Singularity Problem](http://arxiv.org/abs/hep-th/9204096v1) | John Ellis, N. E. Mavromatos, D. V. Nanopoulos | 1992-04-29 | We argue that the infinitely many gauge symmetries of string theory provide an infinite set of conserved (gauge) quantum numbers (W-hair) which characterise black hole states and maintain quantum coherence, even during exotic processes like black hole evaporation/decay. We study ways of measuring the W-hair of spherically-symmetric four-dimensional objects with event horizons, treated as effectively two-dimensional string black holes. Measurements can be done either through the s-wave scattering of light particles off the string black-hole background, or through interference experiments of Aharonov-Bohm type. We also speculate on the role of the extended W-symmetries possessed by the topological field theories that describe the region of space-time around a singularity. |
| [The Black Hole in Three Dimensional Space Time](http://arxiv.org/abs/hep-th/9204099v3) | Máximo Bañados, Claudio Teitelboim, Jorge Zanelli | 1992-04-29 | The standard Einstein-Maxwell equations in 2+1 spacetime dimensions, with a negative cosmological constant, admit a black hole solution. The 2+1 black hole -characterized by mass, angular momentum and charge, defined by flux integrals at infinity- is quite similar to its 3+1 counterpart. Anti-de Sitter space appears as a negative energy state separated by a mass gap from the continuous black hole spectrum. Evaluation of the partition function yields that the entropy is equal to twice the perimeter length of the horizon. |
| [Statistical Mechanics of Black Holes](http://arxiv.org/abs/hep-th/9205021v1) | B. Harms, Y. Leblanc | 1992-05-11 | We analyze the statistical mechanics of a gas of neutral and charged black holes. The microcanonical ensemble is the only possible approach to this system, and the equilibrium configuration is the one for which most of the energy is carried by a single black hole. Schwarzschild black holes are found to obey the statistical bootstrap condition. In all cases, the microcanonical temperature is identical to the Hawking temperature of the most massive black hole in the gas. U(1) charges in general break the bootstrap property. The problems of black hole decay and of quantum coherence are also addressed. |
| [Stability Analysis of a Stringy Black Hole](http://arxiv.org/abs/hep-th/9205023v1) | Rue-Ron Hsu, Green Huang, Wei-Fu Lin, Chin-Rong Lee | 1992-05-12 | We investigate the stability of charged black holes in two-dimensional heterotic string theories that were recently discussed by McGuidan, Nappi and Yost. In the framework of small time-dependent perturbation, we find that these black holes are linearly stable. |
| [Supersymmetry as a Cosmic Censor](http://arxiv.org/abs/hep-th/9205027v1) | Renata Kallosh, Andrei Linde, Tomás Ortín, Amanda Peet, Antoine Van Proeyen | 1992-05-13 | In supersymmetric theories the mass of any state is bounded below by the values of some of its charges. The corresponding bounds in case of Schwarzschild and Reissner-Nordstr\"om black holes are known to coincide with the requirement that naked singularities be absent. Here we investigate charged dilaton black holes in this context. We show that the extreme solutions saturate the supersymmetry bound of $N=4\ d=4$ supergravity, or dimensionally reduced superstring theory. Specifically, we have shown that extreme dilaton black holes, with electric and magnetic charges, admit super-covariantly constant spinors. The supersymmetric positivity bound for dilaton black holes, $M \geq \frac{1}{\sqrt 2}(|Q|+|P|)$, takes care of the absence of naked singularities of the dilaton black holes and is, in this sense, equivalent to the cosmic censorship condition. The temperature, entropy and singularity are discussed. The Euclidean action (entropy) of the extreme black hole is given by $2\pi |PQ|$. We argue that this result, as well as the one for Lorentzian signature, is not altered by higher order corrections in the supersymmetric theory. When a black hole reaches its extreme limit, it cannot continue to evaporate by emitting elementary particles, since this would violate the supersymmetric positivity bound. We speculate on the possibility that an extreme black hole may evaporate" by emitting smaller extreme black holes. |
| [Fadeev-Popov Ghosts and 1+1 Dimensional Black Hole Evaporation](http://arxiv.org/abs/hep-th/9205028v1) | Andrew Strominger | 1992-05-13 | Recently Callan, Giddings, Harvey and the author derived a set of one-loop semiclassical equations describing black hole formation/evaporation in two-dimensional dilaton gravity conformally coupled to $N$ scalar fields. These equations were subsequently used to show that an incoming matter wave develops a black hole type singularity at a critical value $\phi_{cr}$ of the dilaton field. In this paper a modification to these equations arising from the Fadeev-Popov determinant is considered and shown to have dramatic effects for $N<24$, in which case $\phi_{cr}$ becomes complex. The $N<24$ equations are solved along the leading edge of an incoming matter shock wave and found to be non-singular. The shock wave arrives at future null infinity in a zero energy state, gravitationally cloaked by negative energy Hawking radiation. Static black hole solutions supported by a radiation bath are also studied. The interior of the event horizon is found to be non-singular and asymptotic to deSitter space for $N<24$, at least for sufficiently small mass. It is noted that the one-loop approximation is {\it not} justified by a small parameter for small $N$. However an alternate theory (with different matter content) is found for which the same equations arise to leading order in an adjustable small parameter. |
| [Global Analysis of New Gravitational Singularities in String and
Particle Theories](http://arxiv.org/abs/hep-th/9205037v1) | I. Bars, K. Sfetsos | 1992-05-13 | We present a global analysis of the geometries that arise in non-compact current algebra (or gauged WZW) coset models of strings and particles propagating in curved space-time. The simplest case is the 2d black hole. In higher dimensions these geometries describe new and much more complex singularities. For string and particle theories (defined in the text) we introduce general methods for identifying global coordinates and give the general exact solution for the geodesics for any gauged WZW model for any number of dimensions. We then specialize to the 3d geometries associated with $SO(2,2)/SO(2,1)$ (and also $SO(3,1)/SO(2,1)$) and discuss in detail the global space, geodesics, curvature singularities and duality properties of this space. The large-small (or mirror) type duality property is reformulated as an inversion in group parameter space. The 3d global space has two topologically distinct sectors, with patches of different sectors related by duality. The first sector has a singularity surface with the topology of pinched double trousers". It can be pictured as the world sheet of two closed strings that join into a single closed string and then split into two closed strings, but with a pinch in each leg of the trousers. The second sector has a singularity surface with the topology of double saddle", pictured as the world sheets of two infinite open strings that come close but do not touch. We discuss the geodesicaly complete spaces on each side of these surfaces and interpret the motion of particles in physical terms. A cosmological interpretation is suggested and comments are mode on possible physical applications. |
| [Cosmological String Backgrounds from Gauged WZW Models](http://arxiv.org/abs/hep-th/9205046v2) | C. Kounnas, D. Luest | 1992-05-15 | We discuss the four-dimensional target-space interpretation of bosonic strings based on gauged WZW models, in particular of those based on the non-compact coset space $SL(2,{\bf R})\times SO(1,1)^2 /SO(1,1)$. We show that these theories lead, apart from the recently broadly discussed black-hole type of backgrounds, to cosmological string backgrounds, such as an expanding Universe. Which of the two cases is realized depends on the sign of the level of the corresponding Kac-Moody algebra. We discuss various aspects of these new cosmological string backgrounds. |
| [A Non Degenerate Semi-Classical Lagrangian for Dilaton-Gravity in Two
Dimensions](http://arxiv.org/abs/hep-th/9205053v1) | Noureddine Mohammedi | 1992-05-15 | An action for two dimensional gravity conformally coupled to two dilaton-type fields is analysed. Classically, the theory has some exact solutions. These include configurations representing black holes. A semi-classical theory is obtained by assuming that these singular solutions are caused by the collapse of some matter fields. The semi-classical equations of motion reveal then that any generic solution must have a flat geometry. |
| [Quantum-Mechanical Scattering of Charged Black Holes](http://arxiv.org/abs/hep-th/9205061v1) | Jennie Traschen, Robert Ferrel | 1992-05-18 | We describe the quantum mechanical scattering of slowly moving maximally charged black holes. Our technique is to develop a canonical quantization procedure on the parameter space of possible static classical solutions. With this, we compute the capture cross sections for the scattering of two black holes. Finally, we discuss how quantization on this parameter space relates to quantization of the degrees of freedom of the gravitational field. |
| [Edge Currents and Vertex Operators for Chern-Simons Gravity](http://arxiv.org/abs/hep-th/9205077v1) | G. Bimonte, K. S. Gupta, A. Stern | 1992-05-20 | We apply elementary canonical methods for the quantization of 2+1 dimensional gravity, where the dynamics is given by E. Witten's $ISO(2,1)$ Chern-Simons action. As in a previous work, our approach does not involve choice of gauge or clever manipulations of functional integrals. Instead, we just require the Gauss law constraint for gravity to be first class and also to be everywhere differentiable. When the spatial slice is a disc, the gravitational fields can either be unconstrained or constrained at the boundary of the disc. The unconstrained fields correspond to edge currents which carry a representation of the $ISO(2,1)$ Kac-Moody algebra. Unitary representations for such an algebra have been found using the method of induced representations. In the case of constrained fields, we can classify all possible boundary conditions. For several different boundary conditions, the field content of the theory reduces precisely to that of 1+1 dimensional gravity theories. We extend the above formalism to include sources. The sources take into account self- interactions. This is done by punching holes in the disc, and erecting an $ISO(2,1)$ Kac-Moody algebra on the boundary of each hole. If the hole is originally sourceless, a source can be created via the action of a vertex operator $V$. We give an explicit expression for $V$. We shall show that when acting |
| [Grand Canonical Partition Function of a 2-dimensional Hubbard Model](http://arxiv.org/abs/hep-lat/9205024v1) | I. M. Barbour, E. G. Klepfish | 1992-05-26 | We present a new technique for a numerical analysis of the phase structure of the 2D Hubbard model as a function of the hole chemical potential. The grand canonical partition function for the model is obtained via Monte Carlo simulations. The dependence of the hole occupation number on the chemical potential and the temperature is evaluated. These calculations, together with a study of the Yang-Lee zeros of the grand canonical partition function, show evidence of a phase transition at zero temperature and particle density below half-filling. The binding energy of a pair of holes is calculated in the low temperature regime and the possibility for pairing is explored. |
| [About some exact solutions for 2+1 gravity coupled to gauge fields](http://arxiv.org/abs/hep-th/9205095v1) | Ian I. Kogan | 1992-05-26 | Some exact static solutions for Einstein gravity in 2+1 dimensions coupled to abelian gauge field are discussed. Some of these solutions are three-dimensional analogs of the Schwarzschild black holes. The metrics in the regions inside and outside the horison are connected by the changing of the Planck mass sign. |
| [Liouville Models of Black Hole Evaporation](http://arxiv.org/abs/hep-th/9205089v2) | Adel Bilal, Curtis Callan | 1992-05-27 | We construct new theories of dilation gravity coupled to conformal matter which are exact $c=26$ conformal field theories and presumably consistent frameworks for discussing black hole physics in two dimensions. They differ from the CGHS equations in the precise dilaton dependence of the cosmological constant. A further modification proposed by Strominger with a view to eliminating unphysical ghost Hawking radiation is also considered. The new classical equations of motion are explicitly soluble, thus permitting an exact analysis of both static and dynamic senarios. While the static solutions are physically reasonable, the dynamical solutions include puzzling examples with wrong-sign Hawking radiation. We indicate how the latter problem may be resolved in the full quantum theory. |
| [Lattice distortion and energy level structures in doped C_{60} and
C_{70} studied with the extended Su-Schrieffer-Heeger model: Polaron
excitations and optical absorption](http://arxiv.org/abs/cond-mat/9205014v1) | Kikuo Harigaya | 1992-05-27 | We extend the Su-Schrieffer-Heeger model of polyacetylene to C_{60} and C_{70} molecules, and solve numerically. The calculations of the undoped systems agree well with the known results. When the system (C_{60} or C_{70}) is doped with one or two electrons (or holes), the additional charges accumulate almost along an equatorial line of the molecule. The dimerization becomes weaker almost along the same line. Two energy levels intrude largely in the gap. The intrusion is larger in C_{70} than in C_{60}. Therefore, polarons'' are predicted in doped buckminster- fullerenes. We calculate optical absorption coefficient for C_{60} in order to look at how polarons'' will be observed. It is predicted that there appears a new peak at the lower energy than the intergap transition peaks. It is also found that C_{60} and C_{70} are related mutually with respect to electronical structures as well as lattice geometries. (to be published in Phys. Rev. B 45, June 15 issue) |
| [Matching Conditions and Gravitational Collapse in Two-Dimensional
Gravity](http://arxiv.org/abs/hep-th/9205098v1) | R. B. Mann, S. F. Ross | 1992-05-27 | The general theory of matching conditions is developed for gravitational theories in two spacetime dimensions. Models inspired from general relativity and from string theory are considered. These conditions are used to study collapsing dust solutions in spacetimes with non-zero cosmological constant, demonstrating how two-dimensional black holes can arise as the endpoint of such collapse processes. |
| [Information Loss and Anomalous Scattering](http://arxiv.org/abs/hep-th/9205114v2) | Amanda Peet, Leonard Susskind, Larus Thorlacius | 1992-05-30 | The approach of 't Hooft to the puzzles of black hole evaporation can be applied to a simpler system with analogous features. The system is $1+1$ dimensional electrodynamics in a linear dilaton background. Analogues of black holes, Hawking radiation and evaporation exist in this system. In perturbation theory there appears to be an information paradox but this gets resolved in the full quantum theory and there exists an exact $S$-matrix, which is fully unitary and information conserving. 't Hooft's method gives the leading terms in a systematic approximation to the exact result. |
| [Symmetries of String Effective Action and Space-Time Geometry](http://arxiv.org/abs/hep-th/9206017v1) | S. Pratik Khastgir, Jnanadeva Maharana | 1992-06-02 | Two dimensional charged black hole solution is obtained by implementing an $O(2,2)$ transformation on the three dimensional black string solution. Two different monopole backgrounds in five dimensions are related through an $O(2,2)$ transformation. It has been shown in these examples that the particular $O(2,2)$ transformation corresponds to duality transformation. |
| [Dilaton-Axion hair for slowly rotating Kerr black holes](http://arxiv.org/abs/hep-th/9206018v1) | S. Mignemi, N. R. Stewart | 1992-06-04 | Campbell et al. demonstrated the existence of axion hair'' for Kerr black holes due to the non-trivial Lorentz Chern-Simons term and calculated it explicitly for the case of slow rotation. Here we consider the dilaton coupling to the axion field strength, consistent with low energy string theory and calculate the dilaton hair'' arising from this specific axion source. |
| [Black Hole Physics from Liouville Theory](http://arxiv.org/abs/hep-th/9206020v2) | S. P. de Alwis | 1992-06-04 | In a previous paper it was shown that the quantum consistency conditions for the dilaton-gravity theory of Callan et al., imply that the cosmological constant term undergoes a dilaton dependent renormalization, in such a manner that the theory can be written as a Liouville-like theory. In this paper we discuss the physical interpretation of the solutions of this theory. In particular we demonstrate explicitly how quantum corrections tame the black hole singularity. Also under the assumption that in asymptotically Minkowski coordinates, there are no incoming or outgoing ghosts, we show that the Hawking radiation rate is independent of the number of matter fields and is determined by the ghost conformal anomaly. |
| [Conservation Laws and 2D Black Holes in Dilaton Gravity](http://arxiv.org/abs/hep-th/9206044v1) | R. B. Mann | 1992-06-10 | A very general class of Lagrangians which couple scalar fields to gravitation and matter in two spacetime dimensions is investigated. It is shown that a vector field exists along whose flow lines the stress-energy tensor is conserved, regardless of whether or not the equations of motion are satisfied or if any Killing vectors exist. Conditions necessary for the existence of Killing vectors are derived. A new set of 2D black hole solutions is obtained for one particular member within this class of Lagrangians. One such solution bears an interesting resemblance to the 2D string-theoretic black hole, yet contains markedly different thermodynamic properties. |
| [Conformally Exact Results for SL(2,R)\times SO(1,1)^{d-2}/SO(1,1) Coset
Models](http://arxiv.org/abs/hep-th/9206048v1) | Konstadinos Sfetsos | 1992-06-10 | Using the conformal invariance of the $SL(2,R)\otimes SO(1,1)^{d-2}/SO(1,1)$ coset models we calculate the conformally exact metric and dilaton, to all orders in the $1/k$ expansion. We consider both vector and axial gauging. We find that these cosets represent two different space--time geometries: ($2d$ black hole)$\otimes \IR^{d-2}$ for the vector gauging and ($3d$ black string)$\otimes \IR^{d-3}$ for the axial one. In particular for $d=3$ and for the axial gauging one obtains the exact metric and dilaton of the charged black string model introduced by Horne and Horowitz. If the value of $k$ is finite we find two curvature singularities which degenerate to one in the semi--classical $k\to \infty$ limit. We also calculate the reflection and transmission coefficients for the scattering of a tachyon wave and using the Bogoliubov transformation we find the Hawking temperature. |
| [Two Dimensional String Theory And Black Holes](http://arxiv.org/abs/hep-th/9206069v1) | Edward Witten | 1992-06-17 | This lecture surveys a few loosely related topics, ranging from the scarcity of quantum field theories -- and the role that this has played, and still plays, in physics -- to paradoxes involving black holes in soluble two dimensional string theory and the question of whether naked singularities might be of even greater interest to string theorists than black holes. |
| [The Endpoint of Hawking Evaporation](http://arxiv.org/abs/hep-th/9206070v1) | J. Russo, L. Susskind, L. Thorlacius | 1992-06-17 | The formation and semi-classical evaporation of two-dimensional black holes is studied in an exactly solvable model. Above a certain threshold energy flux, collapsing matter forms a singularity inside an apparent horizon. As the black hole evaporates the apparent horizon recedes and meets the singularity in a finite proper time. The singularity emerges naked and future evolution of the geometry requires boundary conditions to be imposed there. There is a natural choice of boundary conditions which match the evaporated black hole solution onto the linear dilaton vacuum. Below the threshold energy flux no horizon forms and boundary conditions can be imposed where infalling matter is reflected from a time-like naked singularity. All information is recovered at spatial infinity in this case. |
| [Uniqueness of the Axionic Kerr Black Hole](http://arxiv.org/abs/hep-th/9206068v1) | Rue-Ron Hsu, Green Huang, Wei-Fu Lin | 1992-06-17 | Under the axisymmetry and under the invarance of simultaneous inversion of time and azimuthal angle, we show that the axionic Kerr black hole is the ${\it unique}$ stationary solution of the minimal coupling theory of gravity and the Kalb-Ramond field, which has a regular event horizon, is asymptotically flat and has a finite axion field strength at event horizon. |
| [Quantum Theory of Dilaton Gravity in 1+1 Dimensions](http://arxiv.org/abs/hep-th/9206071v1) | K. Hamada | 1992-06-18 | We discuss the quantum theory of 1+1 dimensional dilaton gravity, which is an interesting model with analogous features to the spherically symmetric gravitational systems in 3+1 dimensions. The functional measures over the metrics and the dilaton field are explicitly evaluated and the diffeomorphism invariance is completely fixed in conformal gauge by using the technique developed in the two dimensional quantum gravity. We argue the relations to the ADM formalism. The physical state conditions reduce to the usual Wheeler-DeWitt equations when the dilaton $\df^2 ~ (=\e^{-2\phi}) $ is large enough compared with $\kappa =(N-51/2)/12$, where $N $ is the number of matter fields. This corresponds to the large mass limit in the black hole geometry. A singularity appears at $\df^2 =\kappa (>0) $. The final stage of the black hole evaporation corresponds to the region $\df^2 \sim \kappa $, where the Liouville term becomes important, which just comes from the measure of the metrics. If $\kappa < 0 $, the singularity disappears. |
| [World-Sheet Duality, Space-Time Foam, and the Quantum Fate of a Stringy
Black Hole](http://arxiv.org/abs/hep-th/9206077v2) | John Ellis, N. E. Mavromatos, D. V. Nanopoulos | 1992-06-19 | We interpret Minkowski black holes as world-sheet {\it spikes } which are related by world-sheet { \it duality} to {\it vortices } that correspond to Euclidean black holes. These world-sheet defects induce defects in the gauge fields of the corresponding coset Wess-Zumino descriptions of spherically-symmetric black holes. The low-temperature target space-time foam is a Minkowski black hole (spike) plasma with confined Euclidean black holes (vortices). The high-temperature phase is a {\it dense} vortex plasma described by a topological gauge field theory on the world-sheet, which possesses enhanced symmetry as in the target space-time singularity at the core of a black hole. Quantum decay via higher-genus effects induces a back-reaction which causes a Minkowski black hole to lose mass until it is indistinguishable from intrinsic fluctuations in the space-time foam. |
| [Charged Dilatonic Black Hole and Hawking Radiation in Two Dimensions](http://arxiv.org/abs/hep-th/9206087v1) | Shin'ichi Nojiri, Ichiro Oda | 1992-06-24 | We consider Callan, Giddings, Harvey and Strominger's (CGHS) two dimensional dilatonic gravity with electromagnetic interactions. This model can be also solved classically. Among the solutions describing static black holes, there exist extremal solutions which have zero temperatures. In the extremal solutions, the space-time metric is not singular. We also obtain the solutions describing charged matter (chiral fermions) collapsing into black holes. Through the collapsing, not only future horizon but past horizon is also shifted. The quantum corrections including chiral anomaly are also discussed. In a way similar to CGHS model, the curvature singularity also appeared, except extremal case, when the matter collapsing. The screening effects due to the chiral anomaly have a tendency to cloak the singularity |
| [String Theory, Black Holes, and SL(2,R) Current Algebra](http://arxiv.org/abs/hep-th/9206107v1) | Shyamoli Chaudhuri, Joseph D. Lykken | 1992-06-29 | We analyse in detail the $SL(2,R)$ black hole by extending standard techniques of Kac-Moody current algebra to the non-compact case. We construct the elements of the ground ring and exhibit W-infinity type structure in the fusion algebra of the discrete states. As a consequence, we can identify some of the exactly marginal deformations of the black hole. We show that these deformations alter not only the spacetime metric but also turn on non-trivial backgrounds for the tachyon and all of the massive modes of the string. |
| [Exactly Solvable Models of 2d Dilaton Quantum Gravity](http://arxiv.org/abs/hep-th/9207006v1) | A. Mikovic | 1992-07-02 | We study canonical quantization of a class of 2d dilaton gravity models, which contains the model proposed by Callan, Giddings, Harvey and Strominger. A set of non-canonical phase space variables is found, forming an $SL(2,{\bf R}) \times U(1)$ current algebra, such that the constraints become quadratic in these new variables. In the case when the spatial manifold is compact, the corresponding quantum theory can be solved exactly, since it reduces to a problem of finding the cohomology of a free-field Virasoro algebra. In the non-compact case, which is relevant for 2d black holes, this construction is likely to break down, since the most general field configuration cannot be expanded into Fourier modes. Strategy for circumventing this problem is discussed. |
| [Low voltage conductance of small tunnel junctions](http://arxiv.org/abs/cond-mat/9207007v1) | F. Guinea, M. Ueda | 1992-07-06 | A discrete charge transfer in a small tunnel junction where Coulomb interactions are important can excite electron-hole pairs near the Fermi level. We use a simple model to study the associated nonequilibrium properties and found two novel effects: (i) for junctions with electrodes of the same electronic properties, a leakage current exists within the Coulomb gap even when the environmental impedance is infinite; (ii) for junctions with electrodes of different electronic properties, the differential conductance diverges when a net interaction between conduction electrons is attractive, and it is strongly suppressed for a net repulsive interaction. |
| [One-Loop Renormalization in Two-Dimensional Matter-Dilaton Quantum
Gravity and Charged Black Holes](http://arxiv.org/abs/hep-th/9207046v1) | E. Elizalde, S. D. Odintsov | 1992-07-14 | The quantum properties of two-dimensional matter-dilaton gravity ---which includes a large family of actions for two-dimensional gravity (in particular, string-inspired models)--- are investigated. The one-loop divergences in linear covariant gauges are calculated and the structure of the one-loop renormalization is studied. The explicit forms of the dilaton potential, dilaton-Maxwell, and dilaton-scalar couplings for which the theory is one-loop multiplicatively renormalizable are found. A comparison with the one-loop renormalization structure of four-dimensional gravity-matter theory is given. Charged multiple-horizon black holes which appear in the model are also considered. |
| [Electric Magnetic Duality in String Theory](http://arxiv.org/abs/hep-th/9207053v2) | Ashoke Sen | 1992-07-15 | The electric-magnetic duality transformation in four dimensional heterotic string theory discussed by Shapere, Trivedi and Wilczek is shown to be an exact symmetry of the equations of motion of low energy effective field theory even after including the scalar and the vector fields, arising due to compactification, in the effective field theory. Using this duality transformation we construct rotating black hole solutions in the effective field theory carrying both, electric and magnetic charges. The spectrum of extremal magnetically charged black holes turns out to be similar to that of electrically charged elementary string excitations. We also discuss the possibility that the duality symmetry is an exact symmetry of the full string theory under which electrically charged elementary string excitations get exchanged with magnetically charged soliton like solutions. This proposal might be made concrete following the suggestion of Dabholkar et. al. that fundamental strings may be regarded as soliton like classical solutions in the effective field theory. |
| [Vortex motion and the Hall effect in type II superconductors: a time
dependent Ginzburg-Landau theory approach](http://arxiv.org/abs/cond-mat/9207018v1) | Alan T. Dorsey | 1992-07-15 | Vortex motion in type II superconductors is studied starting from a variant of the time dependent Ginzburg-Landau equations, in which the order parameter relaxation time is taken to be complex. Using a method due to Gor'kov and Kopnin, we derive an equation of motion for a single vortex ($B\ll H_{c2}$) in the presence of an applied transport current. The imaginary part of the relaxation time and the normal state Hall effect both break particle-hole symmetry,'' and produce a component of the vortex velocity parallel to the transport current, and consequently a Hall field due to the vortex motion. Various models for the relaxation time are considered, allowing for a comparison to some phenomenological models of vortex motion in superconductors, such as the Bardeen-Stephen and Nozi\eres-Vinen models, as well as to models of vortex motion in neutral superfluids. In addition, the transport energy, Nernst effect, and thermopower are calculated for a single vortex. Vortex bending and fluctuations can also be included within this description, resulting in a Langevin equation description of the vortex motion. The Langevin equation is used to discuss the propagation of helicon waves and the diffusional motion of a vortex line. The results are discussed in light of the rather puzzling sign change of the Hall effect which has been observed in the mixed state of the high temperature superconductors. |
| The vacuum polarization around an axionic stringy black hole | A. Carlini, A. Treves, F. Fucito, M. Martellini | 1992-07-16 | We consider the effect of vacuum polarization around the horizon of a 4 dimensional axionic stringy black hole. In the extreme degenerate limit ($Q_a=M$), the lower limit on the black hole mass for avoiding the polarization of the surrounding medium is $M\gg (10^{-15}\div 10^{-11})m_p$ ($m_p$ is the proton mass), according to the assumed value of the axion mass ($m_a\simeq (10^{-3}\div 10^{-6})~eV$). In this case, there are no upper bounds on the mass due to the absence of the thermal radiation by the black hole. In the nondegenerate (classically unstable) limit ($Q_a<M$), the black hole always polarizes the surrounding vacuum, unless the effective cosmological constant of the effective stringy action diverges. |
| Duality in Multi-layered Quantum Hall Systems | C. Ting | 1992-07-17 | The braid group dynamics captures the fractional quantum Hall effect (FQHE) as a manifestation of puncture phase. When the dynamics is generalized for particles on a multi-sheeted surface, we obtain new tools which determine the fractional charges, the quantum statistics, and the filling factors of the multi-layered FQHE. A many-quasi-hole wavefunction is proposed for the bilayered samples. We also predict a $\nu = 5/7$ FQHE for triple-layered samples. The viability of {\em 3-dimensional} FQHE and the application of the concept of generalized duality to anyonic superconductivity are discussed. |
| Mutual statistics, braid group, and the fractional quantum Hall effect | C. Ting | 1992-07-17 | We show that the notion of mutual statistics arises naturally from the representation theory of the braid group over the multi-sheeted surface. A Hamiltonian which describes particles moving on the double-sheeted surface is proposed as a model for the bilayered fractional quantum Hall effect (FQHE) discovered recently. We explicitly show that the quasi-holes of the bilayered Hall fluid display fractional mutual statistics. A model for 3-dimensional FQHE using the multi-layered sample is suggested. |
| Semi-classical Approach to Charged Dilatonic Black Hole in Two
Dimensions | Shin’ichi Nojiri, Ichiro Oda | 1992-07-22 | We consider exactly solvable semi-classical theory of two dimensional dilatonic gravity with electromagnetic interactions. As was done in the paper by Russo, Susskind and Thorlacius, the term which changes the kinetic term is added to the action. The theory contains massless fermions as matter fields and there appear the quantum corrections including chiral anomaly. The screening effect due to the chiral anomaly has a tendency to cloak the singularity. In a region of the parameter space, the essential behavior of the theory is similar to that of Callan, Giddings, Harvey and Strominger’s dilatonic black hole theory modified in the paper by Russo, Susskind and Thorlacius and the singularity formed by the collapsing matter emerges naked. We find, however, another region of the parameter space where the singularity disappears in a finite proper time. Furthermore, in the region of the parameter space, there appears a discontinuity in the metric on the trajectory of the collapsing matter, which would be a signal of topology change |
| Dilatonic Black Holes, Naked Singularities and Strings | P. H. Cox, B. Harms, Y. Leblanc | 1992-07-23 | We extend a previous calculation which treated Schwarschild black hole horizons as quantum mechanical objects to the case of a charged, dilaton black hole. We show that for a unique value of the dilaton parameter a', which is determined by the condition of unitarity of the S matrix, black holes transform at the extremal limit into strings. |
| [The No-Hair Theorem for the Abelian Higgs Model](http://arxiv.org/abs/gr-qc/9207008v1) | Amitabha Lahiri | 1992-07-27 | We consider the general procedure for proving no-hair theorems for static, spherically symmetric black holes. We apply this method to the abelian Higgs model and find a proof of the no-hair conjecture that circumvents the objections raised against the original proof due to Adler and Pearson. |
| [The Dirac Equation Is Separable On The Dyon Black Hole Metric](http://arxiv.org/abs/gr-qc/9207010v1) | İbrahim Semiz | 1992-07-28 | Using the tetrad formalism, we carry out the separation of variables for the massive complex Dirac equation in the gravitational and electromagnetic field of a four-parameter (mass, angular momentum, electric and magnetic charges) black hole. |
| [String Theory Modifies Quantum Mechanics](http://arxiv.org/abs/hep-th/9207103v2) | John Ellis, N. E. Mavromatos, D. V. Nanopoulos | 1992-07-29 | We argue that the light particles in string theory obey an effective quantum mechanics modified by the inclusion of a quantum-gravitational friction term, induced by unavoidable couplings to unobserved massive string states in the space-time foam. This term is related to the $W$-symmetries that couple light particles to massive solitonic string states in black hole backgrounds, and has a formal similarity to simple models of environmental quantum friction. It increases apparent entropy, and may induce the wave functions of macroscopic systems to collapse. |
| [Black Holes from Nucleating Strings](http://arxiv.org/abs/hep-ph/9208212v1) | Jaume Garriga, Alexander Vilenkin | 1992-08-06 | We evaluate the probability that a loop of string that has spontaneously nucleated during inflation will form a black hole upon collapse, after the end of inflation. We then use the observational bounds on the density of primordial black holes to put constraints on the parameters of the model. Other constraints from the distortions of the microwave background and emission of gravitational radiation by the loops are considered. Also, observational constraints on domain wall nucleation and monopole pair production during inflation are briefly discussed. |
| [Thermodynamics of Two-Dimensional Black-Holes](http://arxiv.org/abs/gr-qc/9208002v1) | Chiara R. Nappi, Andrea Pasquinucci | 1992-08-11 | We explore the thermodynamics of a general class of two dimensional dilatonic black-holes. A simple prescription is given that allows us to compute the mass, entropy and thermodynamic potentials, with results in agreement with those obtained by other methods, when available. |
| [Gravitationally Collapsing Dust in $(2+1)$ Dimensions](http://arxiv.org/abs/hep-th/9208036v1) | S. F. Ross, R. B. Mann | 1992-08-13 | We investigate the circumstances under which gravitationally collapsing dust can form a black hole in three-dimensional spacetime. |
| [The Last Three Minutes: Issues in Gravitational Wave Measurements of
Coalescing Compact Binaries](http://arxiv.org/abs/astro-ph/9208005v1) | Curt Cutler, Theocharis A. Apostolatos, Lars Bildsten, Lee Samuel Finn, Eanna E. Flanagan, Daniel Kennefick, Dragoljubov M. Markovic, Amos Ori, Eric Poisson, Gerald Jay Sussman, Kip S. Thorne | 1992-08-25 | Gravitational-wave interferometers are expected to monitor the last three minutes of inspiral and final coalescence of neutron star and black hole binaries at distances approaching cosmological, where the event rate may be many per year. Because the binary's accumulated orbital phase can be measured to a fractional accuracy $\ll 10^{-3}$ and relativistic effects are large, the waveforms will be far more complex, carry more information, and be far harder to model theoretically than has been expected. Theorists must begin now to lay a foundation for extracting the waves' information. |
| [Binary Black Holes in Stationary Orbits](http://arxiv.org/abs/astro-ph/9208006v1) | Sandip K. Chakrabarti | 1992-08-27 | We show that under certain astrophysical conditions a binary system consisting of two compact objects can be stabilized against indefinite shrinking of orbits due to the emission of gravitational radiation. In this case, the lighter binary companion settles down to a stable orbit when the loss of the angular momentum due to gravitational radiation becomes equal to its gain from the accreting matter from the disk around the more massive primary. We claim that such systems can be stable against small perturbations and can be regarded as steady emitters of gravitational waves of constant frequency and amplitude. Furthermore, X-rays emitted by the secondary can also produce astrophysically interesting situations when coupled with gravitational lensing and Doppler effects. |
| [Statistical Mechanics of Extended Black Objects](http://arxiv.org/abs/hep-th/9208070v1) | B. Harms, Y. Leblanc | 1992-08-27 | We extend the considerations of a previous paper on black hole statistical mechanics to the case of black extended objects such as black strings and black membranes in 10-dimensional space-time. We obtain a general expression for the Euclidean action of quantum black p-branes and derive their corresponding degeneracy of states. The statistical mechanics of a gas of black p-branes is then analyzed in the microcanonical ensemble. As in the case of black holes, the equilibrium state is not thermal and the stable configuration is the one for which a single black object carries most of the energy. Again, neutral black p-branes obey the bootstrap condition and it is then possible to argue that their scattering amplitudes satisfy crossing symmetry. Finally, arguments identifying quantum black p-branes with ordinary quantum branes of different dimensionality are presented. |
| [Electric-Magnetic Duality and Supersymmetry in Stringy Black Holes](http://arxiv.org/abs/hep-th/9208078v1) | Tomás Ortín | 1992-08-31 | We present a generalization of the $U(1)^{2}$ charged dilaton black holes family whose main feature is that both $U(1)$ fields have electric and magnetic charges, the axion field still being trivial. We show the supersymmetry of these solutions in the extreme case, in which the corresponding generalization of the Bogomolnyi bound is saturated and a naked singularity is on the verge of being visible to external observers. Then we study the action of a subset of the $SL(2,R)$ group of electric-magnetic duality rotations that generates a non-trivial axion field on those solutions. This group of transformations is an exact symmetry of the $N=4$ $d=4$ ungauged supergravity equations of motion. It has been argued recently that it could be an exact symmetry of the full effective string theory. The generalization of the Bogomolnyi bound is invariant under the full $SL(2,R)$ and the solutions explicitly rotated are shown to be supersymmetric if the originals are. We conjecture that any $SL(2,R)$ transformation will preserve supersymmetry. |
| [Semiclassical Approach to Black Hole Evaporation](http://arxiv.org/abs/hep-th/9209008v1) | David A. Lowe | 1992-09-02 | Black hole evaporation may lead to massive or massless remnants, or naked singularities. This paper investigates this process in the context of two quite different two dimensional black hole models. The first is the original CGHS model, the second is another two dimensional dilaton-gravity model, but with properties much closer to physics in the real, four dimensional, world. Numerical simulations are performed of the formation and subsequent evaporation of black holes and the results are found to agree qualitatively with the exactly solved modified CGHS models, namely that the semiclassical approximation breaks down just before a naked singularity appears. |
| [Cosmic Censorship in Two-Dimensional Gravity](http://arxiv.org/abs/hep-th/9209012v2) | J. Russo, L. Susskind, L. Thorlacius | 1992-09-04 | A weak version of the cosmic censorship hypothesis is implemented as a set of boundary conditions on exact semi-classical solutions of two-dimensional dilaton gravity. These boundary conditions reflect low-energy matter from the strong coupling region and they also serve to stabilize the vacuum of the theory against decay into negative energy states. Information about low-energy incoming matter can be recovered in the final state but at high energy black holes are formed and inevitably lead to information loss at the semi-classical level. |
| [The String Universe: High $T_c$ Superconductor or Quantum Hall
Conductor?](http://arxiv.org/abs/hep-th/9209013v1) | John Ellis, N. E. Mavromatos, D. V. Nanopoulos | 1992-09-04 | Our answer is the latter. Space-time singularities, including the initial one, are described by world-sheet topological Abelian gauge theories with a Chern-Simons term. Their effective $N=2$ supersymmetry provides an initial fixed point where the Bogomolny bound is saturated on the world-sheet, corresponding to an extreme Reissner-Nordstrom solution in space-time. Away from the singularity the gauge theory has world-sheet matter fields, bosons and fermions, associated with the generation of target space-time. Because the fermions are complex (cf the Quantum Hall Effect) rather than real (cf high-$T_c$ superconductors) the energetically-preferred vacuum is not parity or time-reversal invariant, and the associated renormalization group flow explains the cosmological arrow of time, as well as the decay of real or virtual black holes, with a monotonic increase in entropy. |
| [Results on exact solutions of low energy string theory](http://arxiv.org/abs/gr-qc/9209002v2) | David Garfinkle | 1992-09-05 | A family of solutions to low energy string theory is found. These solutions represent waves traveling along "extremal black strings" |
| [Spin texture in weakly doped $Cu0_2$ planes explaining magnetic
correlation length and Raman scattering experiments](http://arxiv.org/abs/cond-mat/9209007v1) | R. J. Gooding, A. Mailhot | 1992-09-08 | A model of $CuO_2$ planes weakly doped with partially delocalised holes is considered. The effect of such a hole on the background AFM spin texture can be represented by a purely magnetic Hamiltonian $H = - \sum_{(ijk)} (\vec S_i \cdot \vec S_j \times \vec S_k)^2$, where the summation is over the four triangles of a single plaquette. We show that this model of randomly distributed chiral spin defects leads to an in--plane spin correlation length approximately described by $\xi^{-1} (x,T) = \xi^{-1} (0,T) + \xi^{-1} (x,0)$, consistent with neutron scattering experiments on $La_{2-x}Sr_xCuO_4$. Further, this model leads to favourable comparisons with $B_{1g}$ Raman scattering results for the same cuprate system. |
| [Boosting Away Singularities from Conformal String Backgrounds](http://arxiv.org/abs/hep-th/9209052v1) | M. Gasperini, J. Maharana, G. Veneziano | 1992-09-15 | Generalizing our previous work, we show how $O(d,d)$ transformations can be used to "boost away" in new dimensions the physical singularities that occur generically in cosmological and/or black-hole string backgrounds. As an example, we show how a recent model by Nappi and Witten can be made singularity-free via $O(3,3)$ boosts involving a fifth dimension. |
| [Quantum Aspects of Black Holes](http://arxiv.org/abs/hep-th/9209055v1) | J. A. Harvey, A. Strominger | 1992-09-16 | This review is based on lectures given at the 1992 Trieste Spring School on String Theory and Quantum Gravity and at the 1992 TASI Summer School in Boulder, Colorado. |
| [Numerical Study of the Wheatley-Hsu-Anderson Interlayer Tunneling
mechanism of High $T_c$ Superconductivity](http://arxiv.org/abs/cond-mat/9209017v1) | M. Arjunwadkar, G. Baskaran, R. Basu, V. N. Muthukumar | 1992-09-16 | We present results obtained (by exact diagonalization) for the problem of two t-J planes with an interlayer coupling $t_\perp$. Our results for small hole concentrations show that in-plane superconducting correlations are enhanced by $t_\perp$. When the constraint on double occupancy in the t-J model is relaxed, the enhancement disappears. These results illustrate the inter--layer tunneling mechanism for superconductivity. |
| [Do Black Holes Destroy Information?](http://arxiv.org/abs/hep-th/9209058v1) | John Preskill | 1992-09-16 | I review the information loss paradox that was first formulated by Hawking, and discuss possible ways of resolving it. All proposed solutions have serious drawbacks. I conclude that the information loss paradox may well presage a revolution in fundamental physics. (To appear in the proceedings of the International Symposium on Black Holes, Membranes, Wormholes, and Superstrings.) |
| [Quantum Dilaton Gravity in the Light-cone Gauge](http://arxiv.org/abs/hep-th/9209064v1) | Xiang Shen | 1992-09-18 | Recently, models of two-dimensional dilaton gravity have been shown to admit classical black-hole solutions that exhibit Hawking radiation at the semi-classical level. These classical and semi-classical analyses have been performed in conformal gauge. We show in this paper that a similar analysis in the light--cone gauge leads to the same results. Moreover, quantization of matter fields in light--cone gauge can be naturally extended to include quantizing the metric field {\it \a la} KPZ. We argue that this may provide a new framework to address many issues associated to black-hole physics. |
| Photoinduced charge separation in Q1D heterojunction materials: Evidence
for electron-hole pair separation in mixed-halide $MX$ solids | L. A. Worl, S. C. Huckett, B. I. Swanson, A. Saxena, A. R. Bishop, J. Tinka Gammel | 1992-09-19 | Resonance Raman experiments on doped and photoexcited single crystals of mixed-halide $MX$ complexes ($M$=Pt; $X$=Cl,Br) clearly indicate charge separation: electron polarons preferentially locate on PtBr segments while hole polarons are trapped within PtCl segments. This polaron selectivity, potentially very useful for device applications, is demonstrated theoretically using a discrete, 3/4-filled, two-band, tight-binding, extended Peierls-Hubbard model. Strong hybridization of the PtCl and PtBr electronic bands is the driving force for separation. |
| Black Holes with a Massive Dilaton | R. Gregory, J. A. Harvey | 1992-09-19 | The modifications of dilaton black holes which result when the dilaton acquires a mass are investigated. We derive some general constraints on the number of horizons of the black hole and argue that if the product of the black hole charge $Q$ and the dilaton mass $m$ satisfies $Q m < O(1)$ then the black hole has only one horizon. We also argue that for $Q m > O(1)$ there may exist solutions with three horizons and we discuss the causal structure of such solutions. We also investigate the possible structures of extremal solutions and the related problem of two-dimensional dilaton gravity with a massive dilaton. |
| Polaron excitations in fullerenes: Theory as pi-conjugated systems | Kikuo Harigaya | 1992-09-20 | We review the recent theoretical treatment of fullerenes as pi-conjugated systems. Polaronic properties due to the Jahn-Teller type effects are mainly discussed. (1) A Su-Schrieffer-Heeger type electron-phonon model is applied to fullerenes: C_60 and C_70, and is solved with the adiabatic approximation to phonons. When the system (C_60 or C_70) is doped with one or two electrons (or holes), the additional charges accumulate along almost an equatorial line of the molecule. The dimerization becomes the weakest along the same line. Two energy levels, the occupied state and the empty state, intrude largely in the gap. The intrusion is larger in C_70 than in C_60. These are polarons'' in doped fullerenes. It is also found that C_60 and C_70 are related mutually with respect to electronical structures as well as lattice geometries. (2) We apply the model to the fullerene epoxide C_60O. It has the polaron-type lattice distortion around the oxygen, and also shows the energy level intrusion in the gap. (3) Optical properties of C_60 are calculated and discussed. In the absorption of the doped molecule, a new peak structure is present owing to the polaronic distortion. In the luminescence of the neutral C_60, the spacing between H_g(8)-phonon side-band peaks and the relative intensities agree well with experiments. In the dispersion of the third harmonic generation, the magnitudes of |chi^(3)| agree with those of experiments at the resonance of the lowest allowed transition as well as in the region away from the resonance. |
| [Detection, Measurement and Gravitational Radiation](http://arxiv.org/abs/gr-qc/9209010v1) | Lee Samuel Finn | 1992-09-24 | Here I examine how to determine the sensitivity of the LIGO, VIRGO, and LAGOS gravitational wave detectors to sources of gravitational radiation by considering the process by which data are analyzed in a noisy detector. By constructing the probability that the detector output is consistent with the presence of a signal, I show how to (1) quantify the uncertainty that the output contains a signal and is not simply noise, and (2) construct the probability distribution that the signal parameterization has a certain value. From the distribution and its mode I determine volumes $V(P)$ in parameter space such that actual signal parameters are in $V(P)$ with probability $P$. If we are {\em designing} a detector, or determining the suitability of an existing detector for observing a new source, then we don't have detector output to analyze but are interested in themost likely’’ response of the detector to a signal. I exploit the techniques just described to determine the most likely'' volumes $V(P)$ for detector output corresponding to the source. Finally, as an example, I apply these techniques to anticipate the sensitivity of the LIGO and LAGOS detectors to the gravitational radiation from a perturbed Kerr black hole. |
| [Domain Walls in $N=1$ Supergravity](http://arxiv.org/abs/hep-th/9209117v2) | Mirjam Cvetic, Stephen Griffies | 1992-09-28 | We discuss a study of domain walls in $N=1, d=4$ supergravity. The walls saturate the Bogomol'nyi bound of wall energy per unit area thus proving stability of the classical solution. They interpolate between two vacua whose cosmological constant is non-positive and in general different. The matter configuration and induced geometry are static. We discuss the field theoretic realization of these walls and classify three canonical configurations with examples. The space-time induced by a wall interpolating between the Minkowski (topology $\Re^{4}$) and anti-de~Sitter (topology $S^{1}(time) \times \Re^{3}(space)$) vacua is discussed. (Comments in chapter 6 on AdS-Minkowski wall induced space-time have been slightly changed) |
| [Dilatonic Supergravity in Two Dimensions and the Disappearance of
Quantum Black Hole](http://arxiv.org/abs/hep-th/9209118v1) | Shin'ichi Nojiri, Ichiro Oda | 1992-09-29 | We analyze a supergravity theory coupled to a dilaton and superconformal matters in two dimensions. This theory is classically soluble and we find all the solutions appeared in Callan, Giddings, Harvey and Strominger's dilatonic gravity also satisfy the constraints and the equations of motion in this supersymmetric theory. We quantize this theory by following the procedure of Distler, Hlousek and Kawai. In the quantum action, the cosmological term is renormalized to vanish. As a result, any solution corresponding to classical black hole does not appear in the quantum theory, which should be compared with the non-supersymmetric case. |
| [$W_{\infty} Algebra in Two-Dimensional Black Hole](http://arxiv.org/abs/hep-th/9209122v1) | T. Eguchi, H. Kanno, S. -K. Yang | 1992-09-29 | We study the $SL(2;R)/U(1)$ coset model of two-dimensional black hole and its relation to the Liouville theory coupled to c=1 matter. We uncover a basic isomorphism in the algebraic structures of these theories and show that the black hole model has the same physical spectrum as the c=1 model, i.e. tachyons, $W_\infty$ currents and the ground ring elements. we also identify the operator responsible for the creation of the mass of the black hole. |
| [Dilaton-Axion Symmetry](http://arxiv.org/abs/hep-th/9209125v1) | John H. Schwarz | 1992-09-29 | The heterotic string compactified on a six-torus is described by a low-energy effective action consisting of N=4 supergravity coupled to N=4 super Yang-Mills, a theory that was studied in detail many years ago. By explicitly carrying out the dimensional reduction of the massless fields, we obtain the bosonic sector of this theory. In the Abelian case the action is written with manifest global $O(6,6+n)$ symmetry. A duality transformation that replaces the antisymmetric tensor field by an axion brings it to a form in which the axion and dilaton parametrize an $SL(2,R)/SO(2)$ coset, and the equations of motion have $SL(2,R)$ symmetry. This symmetry, which combines Peccei--Quinn translations with Montonen--Olive duality transformations, has been exploited in several recent papers to construct black hole solutions carrying both electric and magnetic charge. Our purpose is to explore whether, as various authors have conjectured, an $SL(2,Z)$ subgroup could be an exact symmetry of the full quantum string theory. If true, this would be of fundamental importance, since this group transforms the dilaton nonlinearly and can relate weak and strong coupling. |
| [Spontaneous CP Violation, Small Instanton and Invisible Axion](http://arxiv.org/abs/hep-ph/9209295v1) | Soo-Jong Rey | 1992-09-30 | I propose a variant invisible axion model of spontaneous CP violation at the electroweak scale without CP domain wall and `strong CP' problems. Both large size QCD and small size non-QCD instantons break CP and Peccei-Quinn symmetries, and render cosmologically harmful CP domain walls unstable. The decaying epoch depends on size of small instanton effects, and is around 100 eV if the current neutron electric dipole moment bound is maximally saturated. The model satisfies constraints from primordial D and He photo-dissociation and black hole formation, while producing cosmologically interesting size of gravitational waves and galaxy-scale density perturbations. |
| [Poincaré Gauge Theories for Lineal Garvity](http://arxiv.org/abs/gr-qc/9209013v2) | G. Grignani, G. Nardelli | 1992-09-30 | We have shown that two of the most studied models of lineal gravities - Liouville gravity and astring-inspired’’ model exhibiting the main characteristic features of a black-hole solution - can be formulated as gauge invariant theories of the Poincar'e group. The gauge invariant couplings to matter (particles, scalar and spinor fields) and explicit solutions for some matter field configurations, are provided. It is shown that both the models, as well as the couplings to matter, can be obtained as suitable dimensional reductions of a 2+1-dimensional ISO(2,1) gauge invariant theory. |
| The Microcanonical Functional Integral. I. The Gravitational Field | J. David Brown, James W. York | 1992-09-30 | The gravitational field in a spatially finite region is described as a microcanonical system. The density of states $\nu$ is expressed formally as a functional integral over Lorentzian metrics and is a functional of the geometrical boundary data that are fixed in the corresponding action. These boundary data are the thermodynamical extensive variables, including the energy and angular momentum of the system. When the boundary data are chosen such that the system is described semiclassically by {\it any} real stationary axisymmetric black hole, then in this same approximation $\ln\nu$ is shown to equal 1/4 the area of the black hole event horizon. The canonical and grand canonical partition functions are obtained by integral transforms of $\nu$ that lead to “imaginary time” functional integrals. A general form of the first law of thermodynamics for stationary black holes is derived. For the simpler case of nonrelativistic mechanics, the density of states is expressed as a real-time functional integral and then used to deduce Feynman’s imaginary-time functional integral for the canonical partition function. |
| Black Holes Coupled to a Massive Dilaton | J. Horne, G. Horowitz | 1992-10-02 | We investigate charged black holes coupled to a massive dilaton. It is shown that black holes which are large compared to the Compton wavelength of the dilaton resemble the Reissner-Nordstr"om solution, while those which are smaller than this scale resemble the massless dilaton solutions. Black holes of order the Compton wavelength of the dilaton can have wormholes outside the event horizon in the string metric. Unlike all previous black hole solutions, nearly extremal and extremal black holes (of any size) repel each other. We argue that extremal black holes are quantum mechanically unstable to decay into several widely separated black holes. We present analytic arguments and extensive numerical results to support these conclusions. |
| Supersymmetry and Positive Energy in Classical and Quantum
Two-Dimensional Dilaton Gravity | Youngchul Park, Andrew Strominger | 1992-10-02 | An $N = 1$ supersymmetric version of two dimensional dilaton gravity coupled to matter is considered. It is shown that the linear dilaton vacuum spontaneously breaks half the supersymmetries, leaving broken a linear combination of left and right supersymmetries which squares to time translations. Supersymmetry suggests a spinorial expression for the ADM energy $M$, as found by Witten in four-dimensional general relativity. Using this expression it is proven that ${M}$ is non-negative for smooth initial data asymptotic (in both directions) to the linear dilaton vacuum, provided that the (not necessarily supersymmetric) matter stress tensor obeys the dominant energy condition. A {\it quantum} positive energy theorem is also proven for the semiclassical large-$N$ equations, despite the indefiniteness of the quantum stress tensor. For black hole spacetimes, it is shown that $M$ is bounded from below by $e^{- 2 \phi_H}$, where $\phi_H$ is the value of the dilaton at the apparent horizon, provided only that the stress tensor is positive outside the apparent horizon. This is the two-dimensional analogue of an unproven conjecture due to Penrose. Finally, supersymmetry is used to prove positive energy theorems for a large class of generalizations of dilaton gravity which arise in consideration of the quantum theory. |
| Duality Symmetries from Non–Abelian Isometries in String Theories | Xenia C. de la Ossa, Fernando Quevedo | 1992-10-05 | In string theory it is known that abelian isometries in the sigma model lead to target space duality. We generalize this duality to backgrounds with non–abelian isometries. The procedure we follow consists of gauging the isometries of the original action and constraining the field strength $F$ to vanish. This new action generates dual theories by integrating over either the Lagrange multipliers that set F=0 or the gauge fields. We find that this new duality transformation maps spaces with non–abelian isometries to spaces that may have no isometries at all. This suggests that duality symmetries in string theories need to be understood in a more general context without regard to the existence of continuous isometries on the target space (this is also indicated by the existence of duality in string compactifications on Calabi–Yau manifolds which have no continuous isometries). Physically interesting examples to which our formalism apply are the Schwarzschild metric and the 4D charged dilatonic black hole. For these spherically symmetric black holes in four dimensions, the dual backgrounds are presented and explicitly shown to be new solutions of the leading order string equations. Some of these new backgrounds are found to have no continuous isometries (except for time translations) and also have naked singularities. |
| Charged String-like Solutions of Low-energy Heterotic String Theory | Daniel Waldram | 1992-10-06 | Two string-like solutions to the equations of motion of the low-energy effective action for the heterotic string are found, each a source of electric and magnetic fields. The first carries an electric current equal to the electric charge per unit length and is the most general solution which preserves one half of the supersymmetries. The second is the most general charged solution with an event horizon, a black string'. The relationship of the solutions to fundamental, macroscopic heterotic strings is discussed, and in particular it is shown that any stable state of such a fundamental string also preserves one half of the supersymmetries, in the same manner as the first solution. |
| [Strings and QCD?](http://arxiv.org/abs/hep-th/9210045v1) | Joseph Polchinski | 1992-10-08 | Is large-$N$ QCD equivalent to a string theory? Maybe, maybe not. I review various attempts to answer the question. |
| [Black Holes and Solitons in String Theory](http://arxiv.org/abs/hep-th/9210050v1) | Ashoke Sen | 1992-10-09 | In this review, I discuss a general method for constructing classical solutions of the equations of motion arising in the effective low energy string theory, and discuss specific applications of this method. (Based on talks given at the Johns Hopkins Workshop held at Goteborg, June 8-10, 1992, and ICTP Summer Workshop held at Trieste, July 2-3, 1992) |
| [Time-dependent perturbations in two-dimensional String Black Holes](http://arxiv.org/abs/hep-th/9210055v1) | G. A. Diamandis, B. C. Georgalas, X. Maintas, N. E. Mavromatos | 1992-10-09 | We discuss time-dependent perturbations (induced by matter fields) of a black-hole background in tree-level two-dimensional string theory. We analyse the linearized case and show the possibility of having black-hole solutions with time-dependent horizons. The latter exist only in the presence of time-dependent tachyon’ matter fields, which constitute the only propagating degrees of freedom in two-dimensional string theory. For real tachyon field configurations it is not possible to obtain solutions with horizons shrinking to a point. On the other hand, such a possibility seems to be realized in the case of string black-hole models formulated on higher world-sheet genera. We connect this latter result with black hole evaporation/decay at a quantum level.} |
| Superstrings on Curved Spacetimes | Itzhak Bars | 1992-10-15 | In this lecture I summarize recent developments on strings propagating in curved spacetime. Exact conformal field theories that describe gravitational backgrounds such as black holes and more intricate gravitational singularities have been discovered and investigated at the classical and quantum level. These models are described by gauged Wess-Zumino-Witten models, or equivalently current algebra G/H coset models based on non-compact groups, with a single time coordinate. The classification of such models for all dimensions is complete. Furthermore the heterotic superstrings in curved spacetime based on non-compact groups have also been constructed. For many of the $d\le 4$ models the gravitational geometry described by a sigma model has been determined. Some general results outlined here include a global analysis of the geometry and the exact classical geodesics for any G/H model. Moreover, in the quantized theory, the conformally exact metric and dilaton are obtained for all orders in an expansion of $k$ (the central extension). All such models have large-small (or mirror) duality properties which we reformulate as an inversion in group space. To illustrate model building techniques a specific 4-dimensional heterotic string in curved spacetime is presented. Finally the methods for investigating the quantum theory are outlined. The construction and analysis of these models at the classical and quantum level involve some aspects of noncompact groups which are not yet sufficiently well understood. Some of the open problems in the physics and mathematics areas are outlined. |
| A Conformal Affine Toda Model of 2D Black Holes: A Quantum Study of the
Evaporation End-Point | F. Belgiorno, A. S. Cattaneo, M. Martellini, F. Fucito | 1992-10-16 | In this paper we reformulate the dilaton-gravity theory of Callan \etal\ as a new effective conformal field theory which turns out to be a generalization of the so-called $SL_2$-conformal affine Toda (CAT) theory studied some times ago by Babelon and Bonora. We quantize this model, thus keeping in account the dilaton-gravity quantum effects. We then implement a Renormalization Group analysis to study the black hole thermodynamics and the final state of the Hawking evaporation. |
| Gravitational Collapse in 1+1 Dimensions and Quantum Gravity | K. Hamada | 1992-10-19 | We investigate the quantum theory of 1+1 dimensional dilaton gravity, which is an interesting toy model of the black hole dynamics. The functional measures of gravity part are explicitly evaluated and derive the Wheeler-DeWitt like equations as physical state conditions. In ADM formalism the measures are very ambiguous, but in our formalism they are explicitly defined. Then the new features which are not seen in ADM formalism come out. A singularity appears at $\df^2 =\kappa (>0) $, where $\kappa =(N-51/2)/12 $ and $ N$ is the number of matter fields. At the final stage of the black hole evaporation, the Liouville term becomes important, which just comes from the measures of the fields. Behind the singularity the quantum mechanical region $\kappa > \df^2 >0 $ extends, where the sign of the kinetic term in the Wheeler-DeWitt like equation changes. If $\kappa <0 $, the singularity disappears. We briefly discuss the possibility of gravitational tunneling and the issue of the information loss. (Talk given at “YITP Workshop on Theories of Quantum Fields -Beyond Perturbation-“, Kyoto, Japan, 14-17 July 1992. Some misleading arguments in the preprint UT-Komaba 92-7 entitled “Quamtum Theory of Dilaton Gravity in 1+1 Dimensions” are corrected. The several remarks on the quantization are included. The difference from the other quantum theory is clarified. |
| The Dark Side of String Theory: Black Holes and Black Strings | Gary T. Horowitz | 1992-10-21 | Solutions to low energy string theory describing black holes and black strings are reviewed. Many of these solutions can be obtained by applying simple solution generating transformations to the Schwarzschild metric. In a few cases, the corresponding exact conformal field theory is known. Various properties of these solutions are discussed including their global structure, singularities, and Hawking temperature. (This review is based on lectures given at the 1992 Trieste Spring School on String Theory and Quantum Gravity.) |
| Stringy Quantum Effects in 2-Dimensional Black-Hole | Avinash Dhar, Gautam Mandal, Spenta R. Wadia | 1992-10-22 | We discuss the classical 2-dim. black-hole in the framework of the non-perturbative formulation (in terms of non-relativistic fermions) of c=1 string field theory. We identify an off-shell operator whose classical equation of motion is that of tachyon in the classical graviton-dilaton black-hole background. The black-hole singularity' is identified with the fermi surface in the phase space of a single fermion, and as such is a consequence of the semi-classical approximation. An exact treatment reveals that stringy quantum effects wash away the classical singularity. |
| [Correlaction Effects on the Band Gap of Conducting Polymers](http://arxiv.org/abs/cond-mat/9210022v1) | C. Q. Wu | 1992-10-23 | By applying the projection technique to the computation of excitation energies, we study the correlation effects on the band gap of conducting polymers. In the presence of an additional electron or hole, the correlation induces a polarization cloud around the addi- tional particle, which forms a polaron. For the excitation energy of a polaron,there is a competition between a {\it loss} of the correla- tion energy in the ground state and a {\it gain} of polarization energy. For the Hubbard interaction, the {\it loss} of correlation energy is dominant and correlations increase the band gap.However,for long-range interactions, the {\it gain} of polarization energy is dominant and correlations decrease the band gap. Screening the long- range interaction suppresses the {\it gain}of the polarization energy so that correlations again increase the band gap.A small dimerization is always favorable to the correlation effects. For {\it trans}-poly- acetylene, we obtain the on-site repulsion $U=4.4$eV and the nearest- neighbor interaction $V=0.8$ eV. The screening of $\pi$ electrons due to the polarizability of $\sigma$ electrons is quite strong. ** to be published in Phys. Rev. B |
| [Quantum Effects in Black Hole Interiors](http://arxiv.org/abs/gr-qc/9210013v1) | Warren G. Anderson, Patrick R. Brady, Werner Israel, Sharon M. Morsink | 1992-10-23 | The Weyl curvature inside a black hole formed in a generic collapse grows, classically without bound, near to the inner horizon, due to partial absorption and blueshifting of the radiative tail of the collapse. Using a spherical model, we examine how this growth is modified by quantum effects of conformally coupled massless fields. |
| [Is Quantum Spacetime Foam Unstable?](http://arxiv.org/abs/gr-qc/9210017v1) | Ian H. Redmount, Wai-Mo Suen | 1992-10-28 | A very simple wormhole geometry is considered as a model of a mode of topological fluctutation in Planck-scale spacetime foam. Quantum dynamics of the hole reduces to quantum mechanics of one variable, throat radius, and admits a WKB analysis. The hole is quantum-mechanically unstable: It has no bound states. Wormhole wave functions must eventually leak to large radii. This suggests that stability considerations along these lines may place strong constraints on the nature and even the existence of spacetime foam. |
| [Coset Models Obtained by Twisting WZW Models and Stringy Charged Black
Holes in Four Dimensions](http://arxiv.org/abs/hep-th/9210160v2) | David Gershon | 1992-10-31 | We show that several WZW coset models can be obtained by applying O(d,d) symmetry transformations (referred to as twisting) on WZW models. This leads to a conjecture that WZW models gauged by U(1)^n subgroup can be obtained by twisting (ungauged) WZW models. In addition, a class of solutions that describe charged black holes in four dimensions is derived by twisting SL(2,R)\times SU(2) WZW. |
| [All Or Nothing: On the Small Fluctuations of Two-Dimensional
String-Theoretic Black Holes](http://arxiv.org/abs/hep-th/9210165v3) | Gerald Gilbert, Eric Raiten | 1992-10-31 | A comprehensive analysis of small fluctuations about two-dimensional string-theoretic and string-inspired black holes is presented. It is shown with specific examples that two-dimensional black holes behave in a radically different way from all known black holes in four dimensions. For both the $SL(2,R)/U(1)$ black hole and the two-dimensional black hole coupled to a massive dilaton with constant field strength, it is shown that there are a {\it continuous infinity} of solutions to the linearized equations of motion, which are such that it is impossible to ascertain the classical linear response. It is further shown that the two-dimensional black hole coupled to a massive, linear dilaton admits {\it no small fluctuations at all}. We discuss possible implications of our results for the Callan-Giddings-Harvey-Strominger black hole. |
| [Eluding the no-hair conjecture: Black holes in spontaneously broken
gauge theories](http://arxiv.org/abs/hep-th/9211007v2) | Brian R. Greene, Samir D. Mathur, Christopher M. O'Neill | 1992-11-02 | We study regular and black hole solutions to the coupled classical Einstein--Yang-Mills--Higgs system. It has long been thought that black hole solutions in the spontaneously broken phase of such a theory could have no nontrivial field structure outside of the horizon. We first show that the standard black hole no-hair theorem underlying this belief, although true in the abelian setting, does not necessarily extend to the non-abelian case. This indicates the possibility of solutions with non-trivial gauge and Higgs configurations decaying exponentially {\it outside} the horizon. We then find such solutions by numerical integration of the classical equations for the case of $SU(2)$ coupled to a Higgs doublet (the standard model less hypercharge). As a prelude to this work we also study regular and black hole solutions to Einstein--Non-Abelian--Proca theory and as a postscript we briefly discuss the important issue of stability. |
| [Semiclassical Extremal Blackholes](http://arxiv.org/abs/hep-th/9211011v2) | Sandip P. Trivedi | 1992-11-03 | Extremal black holes are studied in a two dimensional model motivated by a dimensional reduction from four dimensions. Their quantum corrected geometry is calculated semiclassically and a mild singularity is shown to appear at the horizon. Extensions of the geometry past the horizon are not unique but there are continuations free from malevolent singularities. A few comments are made about the relevance of these results to four dimensions and to the study of black hole entropy and information loss. |
| [Chern--Simons Gravity from 3+1 Dimensional Gravity](http://arxiv.org/abs/gr-qc/9211001v2) | G. Grignani, G. Nardelli | 1992-11-03 | In the context of a Poincar\'e gauge theoretical formulation, pure gravity in 3+1-dimensions is dimensionally reduced to gravity in 2+1-dimensions with or without cosmological constant $\Lambda$. The dimensional reductions are consistent with the gauge symmetries, mapping ISO(3, 1) gauge transformations into ISO(2,1) ones. One of the reductions leads to Chern-Simons-Witten gravity. The solutions of 2+1-gravity with $\Lambda\le 0$ (in particular the black-hole solution recently found by Banados, Teitelboim and Zanelli) and those of 1+1-dimensional Liouville gravity, are thus mapped into 3+1-dimensional vacuum solutions. |
| [Black Hole Uncertainties](http://arxiv.org/abs/hep-th/9211013v2) | Ulf H. Danielsson | 1992-11-03 | In this work the quantum theory of two dimensional dilaton black holes is studied using the Wheeler De Witt equation. The solutions correspond to wave functions of the black hole. It is found that for an observer inside the horizon, there are uncertainty relations for the black hole mass and a parameter in the metric determining the Hawking flux. Only for a particular value of this parameter, can both be known with arbitrary accuracy. In the generic case there is instead a relation which is very similar to the so called string uncertainty relation. |
| [Entropy and Action of Dilaton Black Holes](http://arxiv.org/abs/hep-th/9211015v2) | Renata Kallosh, Tomas Ortin, Amanda Peet | 1992-11-04 | We present a detailed calculation of the entropy and action of $U(1)~2$ dilaton black holes, and show that both quantities coincide with one quarter of the area of the event horizon. Our methods of calculation make it possible to find an explanation of the rule $S = A/4$ for all static, spherically symmetric black holes studied so far. We show that the only contribution to the entropy comes from the extrinsic curvature term at the horizon, which gives $S = A/4$ independently of the charge(s) of the black hole, presence of scalar fields, etc. Previously, this result did not have a general explanation, but was established on a case-by-case basis. The on-shell Lagrangian for maximally supersymmetric extreme dilaton black holes is also calculated and shown to vanish, in agreement with the result obtained by taking the limit of the expression obtained for black holes with regular horizon.The physical meaning of the entropy is discussed in relation to the issue of splitting of extreme black holes. |
| [Gauge Field Back-reaction on a Black Hole](http://arxiv.org/abs/gr-qc/9211008v1) | David Hochberg, Thomas W. Kephart | 1992-11-05 | The order $\hbar$ fluctuations of gauge fields in the vicinity of a blackhole can create a repulsive antigravity region extending out beyond the renormalized Schwarzschild horizon. If the strength of this repulsive force increases as higher orders in the back-reaction are included, the formation of a wormhole-like object could occur. |
| [Black Hole Remnants and the Information Puzzle](http://arxiv.org/abs/hep-th/9211030v2) | T. Banks, M. O'Loughlin, A. Strominger | 1992-11-05 | Magnetically charged dilatonic black holes have a perturbatively infinite ground state degeneracy associated with an infinite volume throat region of the geometry. A simple argument based on causality is given that these states do not have a description as ordinary massive particles in a low-energy effective field theory. Pair production of magnetic black holes in a weak magnetic field is estimated in a weakly-coupled semiclassical expansion about an instanton and found to be finite, despite the infinite degeneracy of states. This suggests that these states may store the information apparently lost in black hole scattering processes. |
| [Centrifugal’ Force around a Black Hole](http://arxiv.org/abs/astro-ph/9211005v2) | A. Y. Shiekh | 1992-11-08 | Besides having some very interesting perturbatively unstable orbits, it seems that for a Schwarzschild black hole, below $r=3M$, the force always increases inward with increasing angular momentum. Here this previously known result is derived with greater simplicity, and a similar analysis is performed for black holes with angular momentum and charge. |
| Gauge Formulation of the Spinning Black Hole in (2+1)-Dimensional
Anti-de Sitter Space | Daniel Cangemi, Martin Leblanc, Robert B. Mann | 1992-11-09 | We compute the group element of SO(2,2) associated with the spinning black hole found by Ba~nados, Teitelboim and Zanelli in (2+1)-dimensional anti-de Sitter space-time. We show that their metric is built with SO(2,2) gauge invariant quantities and satisfies Einstein’s equations with negative cosmological constant everywhere except at $r=0$. Moreover, although the metric is singular on the horizons, the group element is continuous and possesses a kink there. |
| Black hole formation in $c=1$ String Field Theory | J. Russo | 1992-11-12 | A suggestion on how black holes may appear in Das-Jevicki Collective field theory is given. We study the behaviour of a test' particle when energy is sent into the system. A perturbation moving near the potential barrier can create a large-distance black hole geometry where the seeming curvature singularity is at the position of the barrier. In the simplest static’ case the exact $D=2$ black hole metric emerges. |
| Vacuum Polarisation and the Black Hole Singularity | W. G. Anderson, P. R. Brady, R. Camporesi | 1992-11-13 | In order to investigate the effects of vacuum polarisation on mass inflation singularities, we study a simple toy model of a charged black hole with cross flowing radial null dust which is homogeneous in the black hole interior. In the region $r^2 \ll e^2$ we find an approximate analytic solution to the classical field equations. The renormalized stress-energy tensor is evaluated on this background and we find the vacuum polarisation backreaction corrections to the mass function $m(r)$. Asymptotic analysis of the semiclassical mass function shows that the mass inflation singularity is much stronger in the presence of vacuum polarisation than in the classical case. |
| Interaction and modular invariance of strings on curved manifolds | Stephen Hwang, Patrick Roberts | 1992-11-17 | We review and present new results for a string moving on an $SU(1,1)$ group manifold. We discuss two classes of theories which use discrete representations. For these theories the representations forbidden by unitarity decouple and, in addition, one can construct modular invariant partition functions. The partion functions do, however, contain divergencies due to the time-like direction of the $SU(1,1)$ manifold. The two classes of theories have the corresponding central charges $c=9,6,5,9/2,\ldots$ and $c=9,15,21,27,\ldots$. Subtracting two from the latter series of central charges we get the Gervais-Neveu series $c-2=7,13,19,25$. This suggests a relationship between the $SU(1,1)$ string and the Liouville theory, similar to the one found in the $c=1$ string. Modular invariance is also demonstrated for the principal continous representations. Furthermore, we present new results for the Euclidean coset $SU(1,1)/U(1)$. The same two classes of theories will be possible here and will have central charges $c=8,5,4,\dots$ and $c=8,14,20,26,\ldots$, where the latter class includes the critical 2d black hole. The partition functions for the coset theory are convergent.(Talk presented by S.H. at the 16’th Johns Hopkins’ Workshop, G"oteborg, Sweden, June 8-10, 1992) |
| Neutrino production through hadronic cascades in AGN accretion disks | L. Nellen, K. Mannheim, P. L. Biermann | 1992-11-17 | We consider the production of neutrinos in active galactic nuclei (AGN) through hadronic cascades. The initial, high energy nucleons are accelerated in a source above the accretion disk around the central black hole. From the source, the particles diffuse back to the disk and initiate hadronic cascades. The observable output from the cascade are electromagnetic radiation and neutrinos. We use the observed diffuse background X-ray luminosity, which presumably results {}from this process, to predict the diffuse neutrino flux close to existing limits from the Frejus experiment. The resulting neutrino spectrum is $E^{-2}$ down to the $\GeV$ region. We discuss modifications of this scenario which reduce the predicted neutrino flux. |
| Matrix Models and 2D Critical String Theory –2D Black Hole by c=1
Matrix Model– | Tamiaki Yoneya | 1992-11-18 | (Lecture at the workshop “Basic Problems in String Theory”, Yukawa Institute for Theoretical Physics, Kyoto, October 19-21) In this talk, we first review the possibility of matrix models toward a nonperturbative (critical) string theory. We then discuss whether the $c=1$ matrix model can describe the black hole solution of 2D critical string theory. We show that there exists a class of integral transformations which send the Virasoro condition for the tachyon field around the 2D black hole to that around the linear dilaton vacuum. In particular, we construct an explicit integral formula wihich describes a continuous deformation of the linear dilaton vacuum to the black hole background. |
| Equivalence of BRST cohomologies for 2-d black hole and c=1 Liouville
theory | Hiroshi Ishikawa, Mitsuhiro Kato | 1992-11-18 | We study the relation between the $SL(2,R)/U(1)$ black hole and the $c=1$ Liouville theory. A deformation, which interpolates the BRST operators of both models, is explicitly constructed. This interpolation is isomorphic, and the physical spectrum of the black hole is equivalent to that of the $c=1$ model tensored by a topological $U(1)/U(1)$ model. Some implications of the deformation are discussed. |
| Two-dimensional dilaton gravity in a unitary gauge | A. Mikovic | 1992-11-18 | Reduced phase space formulation of CGHS model of 2d dilaton gravity is studied in en extrinsic time gauge. The corresponding Hamiltonian can be promoted into a Hermitian operator acting in the physical Hilbert space, implying a unitary evolution for the system. Consequences for the black hole physics are discussed. In particular, this manifestly unitary theory rules out the Hawking scenario for the endpoint of the black hole evaporation process. |
| The One Dimensional Matrix Model and String Theory | Sumit R. Das | 1992-11-19 | We discuss the basic features of the double scaling limit of the one dimensional matrix model and its interpretation as a two dimensional string theory. Using the collective field theory formulation of the model we show how the fluctuations of the collective field can be interpreted as the massless “tachyon” of the two dimensional string in a linear dilaton background. We outline the basic physical properties of the theory and discuss the nature of the S-matrix. Finally we show that the theory admits of another interpretation in which a certain integral transform of the collective field behaves as the massless “tachyon” in the two dimensional string with a blackhole background. We show that both the classical background and the fluctuations are non-singular at the black hole singularity. |
| Cauchy horizon singularity without mass inflation | P. R. Brady, D. Nunez, S. Sinha | 1992-11-20 | A perturbed Reissner-Nordstr"om-de Sitter solution is used to emphasize the nature of the singularity along the Cauchy horizon of a charged spherically symmetric black hole. For these solutions, conditions may prevail under which the mass function is bounded and yet the curvature scalar $R{\alpha\beta\gamma\delta} R^{\alpha\beta\gamma\delta}$ diverges. |
| Black Extended Objects, Naked Singularities and P-Branes | B. Harms, Y. Leblanc | 1992-11-24 | We treat the horizons of charged, dilaton black extended objects as quantum mechanical objects. We show that the S matrix for such an object can be written in terms of a p-brane-like action. The requirements of unitarity of the S matrix and positivity of the p-brane tension equivalent severely restrict the number of space-time dimensions and the allowed values of the dilaton parameter a. Generally, black objects transform at the extremal limit into p-branes. |
| Quantum Gravity and Black Hole Dynamics in 1+1 Dimensions | K. Hamada, A. Tsuchiya | 1992-11-30 | We study the quantum theory of 1+1 dimensional dilaton gravity, which is an interesting toy model of the black hole dynamics. The functional measures are explicitly evaluated and the physical state conditions corresponding to the Hamiltonian and the momentum constraints are derived. It is pointed out that the constraints form the Virasoro algebra without central charge. In ADM formalism the measures are very ambiguous, but in our formalism they are explicitly defined. Then the new features which are not seen in ADM formalism come out. A singularity appears at $\df^2 =\kappa (>0) $, where $\kappa =(N-51/2)/12 $ and $ N$ is the number of matter fields. Behind the singularity the quantum mechanical region $\kappa > \df^2 >0 $ extends, where the sign of the kinetic term in the Hamiltonian constraint changes. If $\kappa <0 $, the singularity disappears. We discuss the quantum dynamics of black hole and then give a suggestion for the resolution of the information loss paradox. We also argue the quantization of the spherically symmetric gravitational system in 3+1 dimensions. In appendix the differences between the other quantum dilaton gravities and ours are clarified and our status is stressed. |
| Quantum Models of Black Hole Evaporation | F. Belgiorno, A. S. Cattaneo, F. Fucito, M. Martellini | 1992-11-30 | The discovery of black-hole evaporation represented in many respects a revolutionary event in scientific world; as such, in giving answers to open questions, it gave rise to new problems part of which are still not resolved. Here we want to make a brief review of such problems and examine some possible solutions. Invited Talk at the “Workshop on String Theory, Quantum Gravity and the Unification of the Fundamental Interactions” Rome, September 21-26 |
| Two Dimensional Black Hole Evapolation in the Light-Cone Gauge | Haruhiko Terao | 1992-12-01 | Quantization of the pure $1+1$ dimensional dilaton gravity is examined in the light-cone gauge. It is found that the total action including ghosts generates a $c=0$ free conformal field theory without modification of the classical action, which is required in the conformal gauge. We also study semiclassical equations of the dilaton gravity coupled to $N$ scalar fields. It is shown that the black hole singularity is not removed even for $N<24$ in the light-cone gauge. This indicates that the semiclassical analysis breaks down for small $N$. |
| Topics in String Theory and Quantum Gravity | L. Alvarez-Gaume, M. A. Vazquez-Mozo | 1992-12-01 | These are the lecture notes for the Les Houches Summer School on Quantum Gravity held in July 1992. The notes present some general critical assessment of other (non-string) approaches to quantum gravity, and a selected set of topics concerning what we have learned so far about the subject from string theory. Since these lectures are long (133 A4 pages), we include in this abstract the table of contents, which should help the user of the bulletin board in deciding whether to latex and print the full file. 1-FIELD THEORETICAL APPROACH TO QUANTUM GRAVITY: Linearized gravity; Supergravity; Kaluza-Klein theories; Quantum field theory and classical gravity; Euclidean approach to Quantum Gravity; Canonical quantization of gravity; Gravitational Instantons. 2-CONSISTENCY CONDITIONS: ANOMALIES: Generalities about anomalies; Spinors in 2n dimensions; When can we expect to find anomalies?; The Atiyah-Singer Index Theorem and the computation of anomalies; Examples: Green-Schwarz cancellation mechanism and Witten’s SU(2) global anomaly. 3-STRING THEORY I. BOSONIC STRING: Bosonic string; Conformal Field Theory; Quantization of the bosonic string; Interaction in string theory and the characterization of the moduli space; Bosonic strings with background fields. Stringy corrections to Einstein equations; Toroidal compactifications. $R$-duality; Operator formalism 4-STRING THEORY II. FERMIONIC STRINGS: Fermionic String; Heterotic String; Strings at finite temperature; Is string theory finite? 5-OTHER DEVELOPMENTS AND CONCLUSIONS: String Phenomenology''; Black Holes and Related Subjects |
| [Cosmic Censorship in 2-Dimensional Dilaton Gravity](http://arxiv.org/abs/gr-qc/9212001v1) | Sean A. Hayward | 1992-12-02 | The global structure of 2-dimensional dilaton gravity is studied, attending in particular to black holes and singularities. A gravitational energy is defined and shown to be positive at spatial singularities and negative at temporal singularities. Trapped points are defined, and it is shown that spatial singularities are trapped and temporal singularities are not. Thus a local form of cosmic censorship holds for positive energy. In an analogue of gravitational collapse to a black hole, matter falling into an initially flat space creates a spatial curvature singularity which is cloaked in a spatial or null apparent horizon with non-decreasing energy and area. |
| [Non-Extreme and Ultra-Extreme Domain Walls and Their Global Space-Times](http://arxiv.org/abs/hep-th/9212020v2) | Mirjam Cvetič, Stephen Griffies, Harald H. Soleng | 1992-12-03 | Non-extreme walls (bubbles with two insides) and ultra-extreme walls (bubbles of false vacuum decay) are discussed. Their respective energy densities are higher and lower than that of the corresponding extreme (supersymmetric), planar domain wall. These singularity free space-times exhibit non-trivial causal structure analogous to certain non-extreme black holes. We focus on anti-de~Sitter--Minkowski walls and comment on Minkowski--Minkowski walls with trivial extreme limit, as well as walls adjacent to de~Sitter space-times with no extreme limit. |
| [Quantum Vacuum Instability Near Rotating Stars](http://arxiv.org/abs/gr-qc/9212004v2) | A L Matacz, A C Ottewill, P C W Davies | 1992-12-03 | We discuss the Starobinskii-Unruh process for the Kerr black hole. We show how this effect is related to the theory of squeezed states. We then consider a simple model for a highly relativistic rotating star and show that the Starobinskii-Unruh effect is absent. |
| [Do Black Holes Form?](http://arxiv.org/abs/hep-th/9212034v2) | Richard Gass, Louis Witten | 1992-12-04 | We argue that the collapse of a non-rotating object into a black hole has not been proved to be dynamically stable. There are unstable modes and one should explore whether they may be excited. This paper is withdrawn for revisions and clarification |
| [Cosmological Multi-Black Hole Solutions](http://arxiv.org/abs/hep-th/9212035v2) | David Kastor, Jennie Traschen | 1992-12-04 | We present simple, analytic solutions to the Einstein-Maxwell equation, which describe an arbitrary number of charged black holes in a spacetime with positive cosmological constant $\Lambda$. In the limit $\Lambda=0$, these solutions reduce to the well known Majumdar-Papapetrou (MP) solutions. Like the MP solutions, each black hole in a $\Lambda >0$ solution has charge $Q$ equal to its mass $M$, up to a possible overall sign. Unlike the $\Lambda = 0$ limit, however, solutions with $\Lambda >0$ are highly dynamical. The black holes move with respect to one another, following natural trajectories in the background deSitter spacetime. Black holes moving apart eventually go out of causal contact. Black holes on approaching trajectories ultimately merge. To our knowledge, these solutions give the first analytic description of coalescing black holes. Likewise, the thermodynamics of the $\Lambda >0$ solutions is quite interesting. Taken individually, a $|Q|=M$ black hole is in thermal equilibrium with the background deSitter Hawking radiation. With more than one black hole, because the solutions are not static, no global equilibrium temperature can be defined. In appropriate limits, however, when the black holes are either close together or far apart, approximate equilibrium states are established. |
| [A rotating black hole in the Galactic Center](http://arxiv.org/abs/astro-ph/9212001v1) | Heino Falcke, Peter L. Biermann, Wolfgang J. Duschl, Peter G. Mezger | 1992-12-07 | Recent observations of Sgr A* give strong constraints for possible models of the physical nature of Sgr A* and suggest the presence of a massive black~hole with M<2 10^6 M_sun surrounded by an accretion disk which we estimate to radiate at a luminosity of <7 10^5 L_sun. We therefore calculate the appearance of a standard accretion disk around a Kerr hole in Sgr A* following from general relativity and a few fundamental assumptions. Effective temperature and luminosity of the disk spectra do not depend on the unknown viscosity mechanism but instead are quite sensitive to variations of intrinsic parameters: the mass, the accretion rate, the angular momentum of the accreting hole and the inclination angle. A radiation field of L~7 10^4 - 7 10^5 L_sun and T_eff ~ 2-4 10^4 K can be ascribed to a rapidly rotating Kerr~hole (a>0.9) accreting 10^-8.5 - 10^-7 M_sun/yr at a black~hole mass of M=2 10^6 M_sunseen almost edge on. A low mass black hole of M<10^3 M_sun seems to be very unlikely. We provide aHertzsprung-Russell diagram for black holes’’ together with simple scaling laws to provide an easy-to-handle test for the black hole model. |
| Third Quantization and Black Holes | Michael McGuigan | 1992-12-07 | Recent results on the quantum mechanics of black holes indicate that the spacetime singularity can be avoided if the space of fields is extended in its domain as well as the vanishing of beta functions required as an equation in target space. Such an approach seems to inevitably lead to the quantization in this space that is the so-called third quantization. We discuss some of the implications of third quantization for the physics of blackholes in two dimensions. By discretizing the transverse dimensions describing the horizon it may also be possible to describe regulated four dimensional gravity in this manner and perhaps shed some light on the meaning of black hole entropy. |
| Basis Set Reduction Applied to the Two Dimensional t-Jz Model | Jose Riera, Elbio Dagotto | 1992-12-07 | A simple variation of the Lanczos method is discussed. The new technique is based on a systematic reduction of the size of the Hilbert space of the model under consideration. As an example, the two dimensional ${\rm t-J_z}$ model of strongly correlated electrons is studied. Accurate results for the ground state energy can be obtained on clusters of up to 50 sites, which are unreachable by conventional Lanczos approaches. In particular, the energy of one and two holes is analyzed as a function of ${\rm J_z/t}$. In the bulk limit, it is shown that a finite coupling ${\rm J_z/t ]c} \sim 0.18$ is necessary to induce binding'' of holes in the model. It is argued that this result implies that the two dimensional ${\rm t-J}$ model phase separates only for couplings larger than a $finite$ critical value. |
| [Dynamical Properties of a Single Hole in an Antiferromagnet](http://arxiv.org/abs/cond-mat/9212010v1) | Didier Poilblanc, Timothy Ziman, H. J. Schulz, Elbio Dagotto | 1992-12-07 | A finite size scaling analysis of the spectral function and of the optical conductivity of a single hole moving in an antiferromagnetic background is performed. It is shown that both the low energy quasiparticle peak and the broad higher energy structure are robust with increasing cluster size from $4\times 4$ to $\sqrt{26}\times\sqrt{26}$ sites. In the abscence of spin fluctuations, for most static or dynamical quantities saturation occurs when the size exceeds a characteristic size $N_c(J_z)$. Typically, 16 and 26 site clusters give reliable results for $J_z>0.75$ and $J_z>0.3$ respectively. The hole optical mass is shown to be very large ($>20$) in agreement with the small bandwidth. Due to the energy gap to flip a spin in the vicinity of a hole, a small gap $\propto J_z$ separates the low energy delta-function from the rest of the spectrum in the dynamical correlation functions. On the other hand, with $J_\perp$ this gap seems to disappear with increasing system size as one would expect since the spin waves are gapless in the thermodynamic limit. The large momentum dependence of the quasiparticle weight in the isotropic case is inconsistent with a string picture but agrees well with the self-consistent Born approximation. An accurate estimation of the higher energy part of the spectral functions of the t--J model can be made for momenta close to $(0,0)$ or $(\pi,\pi)$; |
| [CPT Violation in String-Modified Quantum Mechanics and the Neutral Kaon
System](http://arxiv.org/abs/hep-th/9212057v1) | J. Ellis, N. E. Mavromatos, D. V. Nanopoulos | 1992-12-09 | We show that $CPT$ is in general violated in a non-quantum-mechanical way in the effective low-energy theory derived from string theory, as a result of apparent world-sheet charge non-conservation induced by stringy monopoles corresponding to target-space black hole configurations. This modification of quantum mechanics does not violate energy conservation. The magnitude of this effective spontaneous violation of $CPT$ may not be be far from the present experimental sensitivity in the neutral kaon system. We demonstrate that our previously proposed stringy modifications to the quantum-mechanical description of the neutral kaon system violate $CPT$, although in a different way from that assumed in phenomenological analyses within conventional quantum mechanics. We constrain the novel $CPT$-violating parameters using available data on $K_L \rightarrow 2\pi$, $K_S \rightarrow 3\pi ^0$ and semileptonic $K_{L,S}$ decay asymmetries. We demonstrate that these data and an approximate treatment of interference effects in $K \rightarrow 2\pi $ decays are consistent with a {\it non-vanishing} amount of $CPT$ violation at a level accessible to a new round of experiments, and further data and/or analysis are required to exclude the extreme possibility that they dominate over $CP$ violation. Could non-quantum-field theoretical and non-quantum-mechanical $CPT$ violation usher in the long-awaited era of string phenomenology?} |
| [Spin Tunneling, Berry phases and Doped Antiferromagnets](http://arxiv.org/abs/cond-mat/9212018v1) | Assa Auerbach | 1992-12-10 | Interference effects between Berry phase factors in spin tunneling systems have been discussed in recent Letters by Loss, DiVincenzo and Grinstein and von Delft and Henley. This Comment points out that Berry phases in spin tunneling are important in another interesting case: the two dimensional doped antiferromagnet. I show that the dispersion of a single hole in the t-J model changes sign as $e^{2\pi s}$ where $s$ is the size of the spins. This provides an interpretation of the numerical results for the $s=\half$ model, and a prediction for other spin sizes. |
| [Magnetically Charged Black Holes and their Stability](http://arxiv.org/abs/gr-qc/9212009v1) | Peter C. Aichelburg, Piotr Bizon | 1992-12-14 | We study magnetically charged black holes in the Einstein-Yang-Mills-Higgs theory in the limit of infinitely strong coupling of the Higgs field. Using mixed analytical and numerical methods we give a complete description of static spherically symmetric black hole solutions, both abelian and nonabelian. In particular, we find a new class of extremal nonabelian solutions. We show that all nonabelian solutions are stable against linear radial perturbations. The implications of our results for the semiclassical evolution of magnetically charged black holes are discussed. |
| [Black Hole Tunneling Entropy and the Spectrum of Gravity](http://arxiv.org/abs/gr-qc/9212010v1) | A. Casher, F. Englert | 1992-12-15 | The tunneling approach for entropy generation in quantum gravity is applied to black holes. The area entropy is recovered and shown to count only a tiny fraction of the black hole degeneracy. The latter stems from the extension of the wave function outside the barrier. In fact the semi-classical analysis leads to infinite degeneracy. Evaporating black holes leave then infinitely degenerate "planckons" remnants which can neither decay into, nor be formed from, ordinary matter in a finite time. Quantum gravity opens up at the Planck scale into an infinite Hilbert space which is expected to provide the ultraviolet cutoff required to render the theory finite in the sector of large scale physics. |
| [Arbitrary Spacetimes from the SL(2,R)/U(1) Coset Model](http://arxiv.org/abs/hep-th/9212095v1) | N. Mohammedi | 1992-12-16 | We show that the gauged SL(2,R) WZWN model yields arbitrary spacetimes in two dimensions. The c = 1 matter field and the black hole singularity are just two particular cases in these spacetimes. |
| [Classical Solutions in Two-Dimensional String Theory and Gravitational
Collapse](http://arxiv.org/abs/hep-th/9212120v1) | J. G. Russo | 1992-12-20 | A general solution to the $D=2$ 1-loop beta functions equations including tachyonic back reaction on the metric is presented. Dynamical black hole (classical) solutions representing gravitational collapse of tachyons are constructed. A discussion on the correspondence with the matrix-model approach is given. |
| [Nonsingular Lagrangians for Two Dimensional Black Holes](http://arxiv.org/abs/hep-th/9212136v2) | T. Banks, M. O'Loughlin | 1992-12-22 | We introduce a large class of modifications of the standard lagrangian for two dimensional dilaton gravity, whose general solutions are nonsingular black holes. A subclass of these lagrangians have extremal solutions which are nonsingular analogues of the extremal Reissner-Nordstrom spacetime. It is possible that quantum deformations of these extremal solutions are the endpoint of Hawking evaporation when the models are coupled to matter, and that the resulting evolution may be studied entirely within the framework of the semiclassical approximation. Numerical work to verify this conjecture is in progress. We point out however that the solutions with non-negative mass always contain Cauchy horizons, and may be sensitive to small perturbations. |
| [The Escape of Gravitational Radiation from the Field of Massive Bodies](http://arxiv.org/abs/astro-ph/9212005v1) | Richard H. Price, Jorge Pullin, Prasun Kundu | 1992-12-23 | We consider a compact source of gravitational waves of frequency $\omega$, in or near a massive spherically symmetric distribution of matter or a black hole. Recent calculations have led to apparently contradictory results for the influence of the massive body on the propagation of the waves. We show here that the results are in fact consistent and in agreement with thestandard’’ viewpoint in which the high frequency compact source produces the radiation as if in a flat background, and the background curvature affects the propagation of these waves. |
| Charged black holes in effective string theory | S. Mignemi, N. R. Stewart | 1992-12-23 | We investigate the qualitative new features of charged dilatonic black holes which emerge when both the Yang-Mills and Gauss-Bonnet curvature corrections are included in the effective action. We consider perturbative effects by an expansion up to second order in the inverse string tension on the four dimensional Schwarzschild background and determine the backreaction. We calculate the thermodynamical functions and show that for magnetic charge above a critical value, the temperature of the black hole has a maximum and goes to zero for a finite value of the mass. This indicates that the conventional Hawking evaporation law is modified by string theory at a classical level. |
| Stringy Sphalerons and Non-Abelian Black Holes | E. E. Donets, D. V. Gal’Tsov | 1992-12-27 | Static spherically symmetric asymptotically flat particle-like and black hole solutions are constructed within the SU(2) sector of 4-dimensional heterotic string effective action. They separate topologically distinct Yang-Mills vacua and are qualitatively similar to the Einstein-Yang-Mills spha- lerons and non-abelian black holes discussed recently. New solutions possess quantized values of the dilaton charge. |
| On flux phase and Néel antiferromagnetism in the {\em t}-{\em
J}-model}} | I. S. Sandalov, M. Richter | 1992-12-29 | We reanalyse the mathematical formulation of the flux-state problem within the $t$-$J$ model. The analysis of different parametrizations in the functional representation shows that (i) calculations which take into account constraints for the number of on-site-available states are describing quasiparticles in terms of wrong local statistics, and contain gauge non-invariant objects; (ii) application of the projection technique in the slave-boson(fermion) representation reproduces the correct statistics, and is exactly equivalent to the conventional diagram technique for Hubbard operators; (iii) it is necessary to introduce an additional equation for the effective hopping amplitude for the flux phase. With the technique for Hubbard operators, which allows one to separate charge and spin channels we construct the mean-field equations for a flux-like state which coexists with N'eel antiferromagnetism (AF). The formal analysis shows that the equations for real and imaginary parts of the effective hopping amplitude are inconsistent for any $\theta \neq 0$ (including $\theta =\pi /4$ which gives flux 1/2). The hopping amplitude is slightly supressed by exchange renormalization. The N'eel magnetization $m$ decreases with increasing concentration of holes. The region where antiferromagnetism exists is decreasing |
| String Instabilities in Black Hole Spacetimes | C. O. Lousto, N. Sánchez | 1992-12-30 | We study the emergence of string instabilities in $D$ - dimensional black hole spacetimes (Schwarzschild and Reissner - Nordstr\o m), and De Sitter space (in static coordinates to allow a better comparison with the black hole case). We solve the first order string fluctuations around the center of mass motion at spatial infinity, near the horizon and at the spacetime singularity. We find that the time components are always well behaved in the three regions and in the three backgrounds. The radial components are {\it unstable}: imaginary frequencies develop in the oscillatory modes near the horizon, and the evolution is like $(\tau-\tau_0)^{-P}$, $(P>0)$, near the spacetime singularity, $r\to0$, where the world - sheet time $(\tau-\tau_0)\to0$, and the proper string length grows infinitely. In the Schwarzschild black hole, the angular components are always well - behaved, while in the Reissner - Nordstr\o m case they develop instabilities inside the horizon, near $r\to0$ where the repulsive effects of the charge dominate over those of the mass. In general, whenever large enough repulsive effects in the gravitational background are present, string instabilities develop. In De Sitter space, all the spatial components exhibit instability. The infalling of the string to the black hole singularity is like the motion of a particle in a potential $\gamma(\tau-\tau_0)^{-2}$ where $\gamma$ depends on the $D$ spacetime dimensions and string angular momentum, with $\gamma>0$ for Schwarzschild and $\gamma<0$ for Reissner - Nordstr\o m black holes. For $(\tau-\tau_0)\to0$ the string ends trapped by the black hole singularity. |
| On the Mass of Two Dimensional Quantum Black Hole | Tsukasa TADA, Shozo UEHARA | 1993-01-07 | For the two dimensional dilaton-coupled quantum gravity model, we give the local black hole mass, which is an analogue of what was first introduced by Fischler, Morgan and Polchinski in the four dimensional gravitational systems. We analyze the original CGHS model with this local mass and find that the local mass is decreasing in the future direction on the matter shock-wave line, while it stays constant at past null infinity. |
| What is the True Description of Charged Black Holes? | Gary T. Horowitz | 1993-01-12 | If string theory describes nature, then charged black holes are not described by the Reissner-Nordstrom solution. This solution must be modified to include a massive dilaton. In the limit of vanishing dilaton mass, the new solution can be found by a generalization of the Harrison transformation for the Einstein-Maxwell equations. These two solution generating transformations and the resulting black holes are compared. It is shown that the extremal black hole with massless dilaton can be viewed as the square root" of the extremal Reissner-Nordstrom solution. When the dilaton mass is included, extremal black holes are repulsive, and it is energetically favorable for them to bifurcate into smaller holes. (To appear in the Festschrift for Dieter Brill) |
| [Hierarchical wave function, Fock cyclic condition and spin-statistics
relation in the spin-singlet fractional quantum Hall effect](http://arxiv.org/abs/cond-mat/9301015v1) | Dingping Li | 1993-01-13 | We construct the hierarchical wave function of the spin-singlet fractional quantum Hall effect, which turns out to satisfy Fock cyclic condition. The spin-statistics relation of the quasi-particles in the spin-singlet fractional quantum Hall effect is also discussed. Then we use particle-hole conjugation to check the wave function. |
| ["Are Black Holes in Brans-Dicke Theory precisely the same as in General
Relativity?"](http://arxiv.org/abs/gr-qc/9301013v3) | M. Campanelli, C. O. Lousto | 1993-01-14 | We study a three-parameters family of solutions of the Brans-Dicke field equations. They are static and spherically symmetric. We find the range of parameters for which this solution represents a black hole different from the Schwarzschild one. We find a subfamily of solutions which agrees with experiments and observations in the solar system. We discuss some astrophysical applications and the consequences on the "no hair" theorems for black holes. |
| [How Fast Does Information Leak out from a Black Hole?](http://arxiv.org/abs/hep-th/9301058v1) | Jacob D. Bekenstein | 1993-01-15 | Hawking's radiance, even as computed without account of backreaction, departs from blackbody form due to the mode dependence of the barrier penetration factor. Thus the radiation is not the maximal entropy radiation for given energy. By comparing estimates of the actual entropy emission rate with the maximal entropy rate for the given power, and using standard ideas from communication theory, we set an upper bound on the permitted information outflow rate. This is several times the rates of black hole entropy decrease or radiation entropy production. Thus, if subtle quantum effects not heretofore accounted for code information in the radiance, the information that was thought to be irreparably lost down the black hole may gradually leak back out from the black hole environs over the full duration of the hole's evaporation. |
| [Quantum Dots in Strong Magnetic Fields: Stability Criteria for the
Maximum Density Droplet](http://arxiv.org/abs/cond-mat/9301019v1) | A. H. MacDonald, S. -R. Eric Yang, M. D. Johnson | 1993-01-15 | In this article we discuss the ground state of a parabolically confined quantum dots in the limit of very strong magnetic fields where the electron system is completely spin-polarized and all electrons are in the lowest Landau level. Without electron-electron interactions the ground state is a single Slater determinant corresponding to a droplet centered on the minimum of the confinement potential and occupying the minimum area allowed by the Pauli exclusion principle. Electron-electron interactions favor droplets of larger area. We derive exact criteria for the stability of the maximum density droplet against edge excitations and against the introduction of holes in the interior of the droplet. The possibility of obtaining exact results in the strong magnetic field is related to important simplifications associated with broken time-reversal symmetry in a strong magnetic field. |
| [2D Black Holes and 2D Gravity](http://arxiv.org/abs/hep-th/9301073v1) | Farhad Ardalan | 1993-01-18 | \small The SL$(2,R)/U(1)$ coset model, with $U(1)$ an element of the third conjugacy class of $SL(2,R)$ subgroups, is considered. The resulting theory is seen to collapse to a one dimensional field theory of Liouville. Then the 2 dimensional black hole $SL(2,R)/U(1)$, with $U(1)$ a non-compact subgroup boosted by a Lorentz transformation, is considered. In the limit of high boost, the resulting black hole is found to tend to the Liouville field coupled to $a\ C=1$ matter field. The limit of the vertex operators of the 2 dimensional black hole also tend to those of the $C=1$ two dimensional gravity. |
| [Two dimensional black-hole as a topological coset model of c=1 string
theory](http://arxiv.org/abs/hep-th/9301083v1) | S. Mukhi, C. Vafa, E. Frenkel | 1993-01-19 | We show that a special superconformal coset (with $\hat c =3$) is equivalent to $c=1$ matter coupled to two dimensional gravity. This identification allows a direct computation of the correlation functions of the $c=1$ non-critical string to all genus, and at nonzero cosmological constant, directly from the continuum approach. The results agree with those of the matrix model. Moreover we connect our coset with a twisted version of a Euclidean two dimensional black hole, in which the ghost and matter systems are mixed. |
| [Relativistic Ring-Diagram Nuclear Matter Calculations](http://arxiv.org/abs/nucl-th/9301012v1) | M. F. Jiang, R. Machleidt, T. T. S. Kuo | 1993-01-20 | A relativistic extension of the particle-particle hole-hole ring-diagram many-body formalism is developed by using the Dirac equation for single-particle motion in the medium. Applying this new formalism, calculations are performed for nuclear matter. The results show that the saturation density is improved and the equation of state becomes softer as compared to corresponding Dirac-Brueckner-Hartree-Fock calculations. Using the Bonn A potential, nuclear matter is predicted to saturate at an energy per nucleon of --15.30 MeV and a density equivalent to a Fermi momentum of 1.38 fm$^{-1}$, in excellent agreement with empirical information. The compression modulus is 152 MeV at the saturation point. |
| [Phase separation in the large-spin {\it t}-{\it J} model](http://arxiv.org/abs/cond-mat/9301030v1) | Antimo Angelucci, Sandro Sorella | 1993-01-23 | We investigate the phase diagram of the two dimensional {\it t}-{\it J} model using a recently developed technique that allows to solve the mean-field model hamiltonian with a variational calculation. The accuracy of our estimate is controlled by means of a small parameter $1/q$, analogous to the inverse spin magnitude $1/s$ employed in studying quantum spin systems. The mathematical aspects of the method and its connection with other large-spin approaches are discussed in details. In the large-$q$ limit the problem of strongly correlated electron systems turns in the minimization of a total energy functional. We have performed numerically this optimization problem on a finite but large $L\times L$ lattice. For a single hole the static small-polaron solution is stable unless for small values of $J$, where polarons of increasing sizes have lower energy. At finite doping we recover phase separation above a critical $J$ and for any electron density, showing that the Emery {\it et al.} picture represents the semiclassical behaviour of the {\it t}-{\it J} model. Quantum fluctuations are expected to be very important especially in the small $J$ -- small doping region, where phase separation may also be suppressed. |
| [On the Black Hole Background of Two-Dimensional String Theory](http://arxiv.org/abs/hep-th/9301105v1) | S. Chaudhuri, D. Minic | 1993-01-26 | The classical black hole background of two-dimensional string theory is examined after including the effect of the tachyon field. Keeping all terms upto $O(T^2)$, and making no other approximations, the only consistent classical solution to the resulting dilaton-graviton theory is found to be flat spacetime with a nontrivial dilaton. |
| [Black Holes with a Generalized Gravitational Action](http://arxiv.org/abs/gr-qc/9301021v2) | Ming Lu, Mark B. Wise | 1993-01-26 | Microscopic black holes are sensitive to higher dimension operators in the gravitational action. We compute the influence of these operators on the Schwarzschild solution using perturbation theory. All (time reversal invariant) operators of dimension six are included (dimension four operators don't alter the Schwarzschild solution). Corrections to the relation between the Hawking temperature and the black hole mass are found. The entropy is calculated using the Gibbons-Hawking prescription for the Euclidean path integral and using naive thermodynamic reasoning. These two methods agree, however, the entropy is not equal to 1/4 the area of the horizon. |
| [Scaling theory of the Mott-Hubbard metal-insulator transition in one
dimension](http://arxiv.org/abs/cond-mat/9301036v1) | C. A. Stafford, A. J. Millis | 1993-01-27 | We use the Bethe ansatz equations to calculate the charge stiffness $D_{\rm c} = (L/2) d^2 E_0/d\Phi_{\rm c}^2|_{\Phi_{\rm c}=0}$ of the one-dimensional repulsive-interaction Hubbard model for electron densities close to the Mott insulating value of one electron per site ($n=1$), where $E_0$ is the ground state energy, $L$ is the circumference of the system (assumed to have periodic boundary conditions), and $(\hbar c/e)\Phi_{\rm c}$ is the magnetic flux enclosed. We obtain an exact result for the asymptotic form of $D_{\rm c}(L)$ as $L\to \infty$ at $n=1$, which defines and yields an analytic expression for the correlation length $\xi$ in the Mott insulating phase of the model as a function of the on-site repulsion $U$. In the vicinity of the zero temperature critical point U=0, $n=1$, we show that the charge stiffness has the hyperscaling form $D_{\rm c}(n,L,U)=Y_+(\xi \delta, \xi/L)$, where $\delta =|1-n|$ and $Y_+$ is a universal scaling function which we calculate. The physical significance of $\xi$ in the metallic phase of the model is that it defines the characteristic size of the charge-carrying solitons, or {\em holons}. We construct an explicit mapping for arbitrary $U$ and $\xi \delta \ll 1$ of the holons onto weakly interacting spinless fermions, and use this mapping to obtain an asymptotically exact expression for the low temperature thermopower near the metal-insulator transition, which is a generalization to arbitrary $U$ of a result previously obtained using a weak- coupling approximation, and implies hole-like transport for $0<1-n\ll\xi^{-1}$. |
| [Physical Properties of Four Dimensional Superstring Gravity Black Hole
Solutions](http://arxiv.org/abs/hep-th/9301129v2) | B. A. Campbell, N. Kaloper, R. Madden, K. A. Olive | 1993-01-31 | We consider the physical properties of four dimensional black hole solutions to the effective action describing the low energy dynamics of the gravitational sector of heterotic superstring theory. We compare the properties of the external field strengths in the perturbative solution to the full $O(\alpha')$ string effective action equations, to those of exact solutions in a truncated action for charged black holes, and to the Kerr-Newman family of solutions of Einstein-Maxwell theory. We contrast the numerical results obtained in these approaches, and discuss limitations of the analyses. Finally we discuss how the new features of classical string gravity affect the standard tests of general relativity. |
| [Equilibrium Two-Dimensional Dilatonic Spacetimes](http://arxiv.org/abs/hep-th/9302009v1) | Michael Crescimanno | 1993-02-03 | We study two-dimensional dilaton gravity coupled to massless scalar fields for static solutions. In addition to the well known black hole, we find another class of solutions that may be understood as that of the black hole in equilibrium with a radiation bath. We claim that there is a solution that is qualitatively unchanged after including Hawking radiation and back-reaction and is furthermore geodesically complete. We compute the thermodynamics of these spacetimes and their mass. We end with a brief discussion of the linear response about these solutions, its significance to stability and noise and a speculation regarding the endpoint of Hawking evaporation in four dimensions. (plain TeX; one figure, available upon request.) |
| [A Conformal Affine Toda Model of 2D-Black Holes the End-Point State and
the S-Matrix](http://arxiv.org/abs/hep-th/9302011v1) | F. Belgiorno, A. S. Cattaneo, M. Martellini, F. Fucito | 1993-02-03 | In this paper we investigate in more detail our previous formulation of the dilaton-gravity theory by Bilal--Callan--de~Alwis as a $SL_2$-conformal affine Toda (CAT) theory. Our main results are: i) a field redefinition of the CAT-basis in terms of which it is possible to get the black hole solutions already known in the literature; ii) an investigation the scattering matrix problem for the quantum black hole states. It turns out that there is a range of values of the $N$ free-falling shock matter fields forming the black hole solution, in which the end-point state of the black hole evaporation is a zero temperature regular remnant geometry. It seems that the quantum evolution to this final state is non-unitary, in agreement with Hawking's scenario for the black hole evaporation. |
| [Dynamics and Collision of Massive Shells in Curved Backgrounds](http://arxiv.org/abs/gr-qc/9302003v2) | D. Nunez, H. P. de Oliveira, J. Salim | 1993-02-03 | We analyse the dynamics of the collision of two spherical massive shells in a generally spherically symmetric background, obtaining an expression from the conservation law that imposes a constraint between the different parameters involved. We study the light-like limit and make some comparisons of the predictions of our master equation with the results obtained in the case of collision of light-like shells, like the short life of white holes or the mass inflation phenomena. We present some particular cases of the constraint equation. |
| [Quantum Theory of Black Holes](http://arxiv.org/abs/gr-qc/9302006v1) | J. Gegenberg, G. Kunstatter | 1993-02-05 | A solvable 2-dimensional conformally invariant midi-superspace model for black holes is obtained by imposing spherical symmetry in 4-dimensional conformally invariant Einstein gravity. The Wheeler-DeWitt equation for the theory is solved exactly to obtain the unique quantum wave functional for an isolated black hole with fixed mass. By suitably relaxing the boundary conditions, a non-perturbative ansatz is obtained for the wave functional of a black hole interacting with its surroundings. |
| [Hole-hole correlations in the $U=\infty $ limit of the Hubbard model and
the stability of the Nagaoka state](http://arxiv.org/abs/cond-mat/9302011v1) | M. Long, X. Zotos | 1993-02-06 | We use exact diagonalisation in order to study the infinite - $U$ limit of the two dimensional Hubbard model. As well as looking at single-particle correlations, we also study {\it N-particle correlation functions} which compare the relative positions of {\it all} the particles in different models. In particular we study 16 and 18-site clusters and compare the charge correlations in the Hubbard model with those of spinless fermions and hard-core bosons. We find that although low densities of holes favour a `locally-ferromagnetic' fermionic description, the correlations at larger densities resemble those of pure hard-core bosons surprisingly well . |
| [A Unitary S-matrix for 2D Black Hole Formation and Evaporation](http://arxiv.org/abs/hep-th/9302022v1) | Erik Verlinde, Herman Verlinde | 1993-02-07 | We study the black hole information paradox in the context of a two-dimensional toy model given by dilaton gravity coupled to $N$ massless scalar fields. After making the model well-defined by imposing reflecting boundary conditions at a critical value of the dilaton field, we quantize the theory and derive the quantum quantum $S$-matrix for the case that $N$=$24$. This $S$-matrix is unitary by construction, and we further argue that in the semiclassical regime it describes the formation and subsequent Hawking evaporation of two-dimensional black holes. Finally, we note an interesting correspondence between the dilaton gravity $S$-matrix and that of the $c=1$ matrix model. |
| [Black Hole from Black Hole in Two Dimensions](http://arxiv.org/abs/hep-th/9302024v1) | Shin'ichi Nojiri, Ichiro Oda | 1993-02-08 | We present a new class of quantum two dimensional dilaton gravity model, which is described by $SL(2,R)/U(1)$ gauged Wess-Zumino-Witten model deformed by $(1,1)$-operator. We analyze the model by ${1 \over k}$ expansion ($k$ is the level of $SL(2,R)$ Wess-Zumino-Witten model) and we find that the curvature singularity does not appear when $k$ is large and the Bondi mass is bounded from below. Furthermore, the rate of the Hawking radiation in the quantum black hole created by shock wave goes to zero asymptotically and the radiation stops when the Bondi mass vanishes. |
| [Non-Singularity of the Exact Two-Dimensional String Black Hole](http://arxiv.org/abs/hep-th/9302037v2) | Malcolm J. Perry, Edward Teo | 1993-02-09 | We study the global structure of the exact two-dimensional space-time which emerges from string theory. Previous work has shown that in the semi-classical limit, this is a black hole similar to the Schwarzschild solution. However, we find that in the exact case, a new Euclidean region appears "between" the singularity and black hole interior. However the boundary between the Lorentzian and Euclidean regions is a coordinate singularity, which turns out to be a surface of time reflection symmetry in an extended space-time. Thus strings having fallen through the black hole horizon would eventually emerge through another one into a new asymptotically flat region. The maximally extended space-time consists of an infinite number of universes connected by wormholes. There are no singularities present in this geometry. We also calculate the mass and temperature associated with the space-time. |
| [Geometry of the 2+1 Black Hole](http://arxiv.org/abs/gr-qc/9302012v1) | Maximo Banados, Marc Henneaux, Claudio Teitelboim, Jorge Zanelli | 1993-02-10 | The geometry of the spinning black holes of standard Einstein theory in 2+1 dimensions, with a negative cosmological constant and without couplings to matter, is analyzed in detail. It is shown that the black hole arises from identifications of points of anti-de Sitter space by a discrete subgroup of $SO(2,2)$. The generic black hole is a smooth manifold in the metric sense. The surface $r=0$ is not a curvature singularity but, rather, a singularity in the causal structure. Continuing past it would introduce closed timelike lines. However, simple examples show the regularity of the metric at $r=0$ to be unstable: couplings to matter bring in a curvature singularity there. Kruskal coordinates and Penrose diagrams are exhibited. Special attention is given to the limiting cases of (i) the spinless hole of zero mass, which differs from anti-de Sitter space and plays the role of the vacuum, and (ii) the spinning hole of maximal angular momentum . A thorough classification of the elements of the Lie algebra of $SO(2,2)$ is given in an Appendix. |
| [Two-dimensional Black Hole With Torsion](http://arxiv.org/abs/hep-th/9302040v1) | S. N. Solodukhin | 1993-02-10 | The 2D model of gravity with zweibeins $e^{a}$ and the Lorentz connection one-form $\omega^{a}_{\ b}$ as independent gravitational variables is considered and it is shown that the classical equations of motion are exactly integrated in coordinate system determined by components of 2D torsion. For some choice of integrating constant the solution is of the charged black hole type. The conserved charge and ADM mass of the black hole are calculated. |
| [Towards a Nonsingular Universe](http://arxiv.org/abs/gr-qc/9302014v1) | Robert H. Brandenberger | 1993-02-11 | A unified theory of all forces should be nonsingular. In such a unified theory, Einstein's general relativity will be a very low curvature effective theory. At larger curvatures, new terms will become important. The question then arises as to whether it is possible to construct an effective action for gravity which leads to a nonsingular theory. In this work, we construct an effective action for gravity in which all homogenerous and isotropic solutions are nonsingular. In particular, there is neither a big bang nor a big crunch. Preliminary work indicates that our construction provides a theory in which anisotropies decrease at large curvatures, and in which the inside of a black hole is singularity free. |
| [Proof of the Generalized Second Law for Quasistationary Semiclassical
Black Holes](http://arxiv.org/abs/gr-qc/9302017v4) | Valery P. Frolov, Don N. Page | 1993-02-15 | A simple direct explicit proof of the generalized second law of black hole thermodynamics is given for a quasistationary semiclassical black hole. |
| [Dyonic Black Holes in String Theory](http://arxiv.org/abs/hep-th/9302065v3) | Guang-Jiun Cheng, Rue-Ron Hsu, Wei-Fu Lin | 1993-02-15 | An exact solution of the low-energy string theory representing static, spherical symmetric dyonic black hole is found. The solution is labeled by their mass, electric charge, magnetic charge and asymptotic value of the scalar dilaton. Some interesting properties of the dyonic black holes are studied. In particular, the Hawking temperature of dyonic black holes depends on both the electric and magnetic charges, and the extremal ones, which have nonzero electric and magnetic charges, have zero temperature but nonzero entropy. These properties are quite different from those of electrically (or magnetically) charged dilaton black holes found by Gibbons {\it et al.} and Garfinkle {\it et al.}, but are the same as those of the dyonic black holes found by Gibbons and Maeda. After this paper was submitted for publication, D. Wiltshire told us that solutions, eqs.(22)-(28), are related to Gibbons-Maeda dyonic black hole solutions by a coordinate transformation and some parameters reparametization \cite{26}. And, we were also informed that many of our results were previously obtained by Kallosh {\it et al.} \cite{27}. The dyonic black hole solutions, eqs.(22)-(28), are also related to those of reference \cite{27} by another coordinate |
| [Nonsingular 2-D Black Holes and Classical String Backgrounds](http://arxiv.org/abs/hep-th/9302070v4) | Piljin Yi | 1993-02-16 | We study a string-inspired classical 2-D effective field theory with {\it nonsingular} black holes as well as Witten's black hole among its static solutions. By a dimensional reduction, the static solutions are related to the $(SL(2,R)_{k}\otimes U(1))/U(1)$ coset model, or more precisely its $O\bigl((\alpha')^{0}\bigr)$ approximation known as the 3-D charged black string. The 2-D effective action possesses a propagating degree of freedom, and the dynamics are highly nontrivial. A collapsing shell is shown to bounce into another universe without creating a curvature singularity on its path, and the potential instability of the Cauchy horizon is found to be irrelevent in that some of the infalling observers never approach the Cauchy horizon. Finally a $SL(2,R)_{k}/U(1)$ nonperturbative coset metric, found and advocated by R. Dijkgraaf et.al., is shown to be nonsingular and to coincide with one of the charged spacetimes found above. Implications of all these geometries are discussed in connection with black hole evaporation. |
| [Effect of three-particle correlations in low dimensional Hubbard models](http://arxiv.org/abs/cond-mat/9302020v1) | Ted Hsu, Benoit Doucot | 1993-02-16 | A simple approximation which captures some non-perturbative aspects of the one electron Green function of strongly interacting Fermion systems is developed. It provides a way to go one step beyond the usual dilute limit since particle-particle as well as particle-hole scattering are treated on the same footing. Intermediate states are constrained to contain only one particle-hole excitation besides the incoming particle. The Faddeev equations resulting from an exact treatment of this three-body problem are investigated. In one dimension the method is able to show spin and charge decoupling, but does not reproduce the exact nature of power-law singularities. Hey dudes, check out the analytical solution in section III! |
| [Tachyon Splits the (d = 2 String) Black Hole Horizon and Turns it
Singular](http://arxiv.org/abs/hep-th/9302075v2) | S. Kalyana Rama | 1993-02-17 | We present a static solution for $d = 2$ critical string theory including the tachyon $T$ but not its potential $V(T)$. This solution thus incorporates tachyon back reaction and, when $T = 0$, reduces to the black hole solution. When $T \neq 0$ one finds that (1) the Schwarzschild horizon of the above black hole splits into two, resembling Reissner-Nordstrom horizons and (2) the curvature scalar develops new singularities at the horizons. These features, as we argue, will persist even with $V(T)$ present. Some possible methods for removing these singularities are discussed. |
| [Information Consumption by Reissner-Nordstrom Black Holes](http://arxiv.org/abs/hep-th/9302080v1) | A. Strominger, S. P. Trivedi | 1993-02-17 | The low-energy scattering of charged fermions by extremal magnetic Reissner-Nordstrom black holes is analyzed in the large-$N$ and $S$-wave approximations. It is shown that (in these approximations) information is carried into a causally inaccessible region of spacetime, and thereby effectively lost. It is also shown that there is an infinite degeneracy of quantum black hole ground states, orremnants”, which store — but will not reveal — the information. A notable feature of the analysis — not shared by recent analyses of dilatonic black holes — is that the key physical questions can be answered within the weak coupling domain. We regard these results as strong evidence that effective information loss occurs in our universe. |
| Quantum Purity at a Small Price: Easing a Black Hole Paradox | Frank Wilczek | 1993-02-19 | Following Hawking, it is usual to mimic the effect of collapse space-time geometry on quantum fields in a semi-classical approximation by imposing suitable boundary conditions at the origin of coordinates, which effectively becomes a moving mirror. Suitable mirror trajectories induces a close analogue to the radiance of black holes, including a flux of outgoing radiation that appears accurately thermal. If the acceleration of the mirror eventually ceases the complete state of the radiation field is a pure quantum state, even though it is indistinguishable from an accurately thermal state for an arbitrarily long period of time and in a precise sense differs little from pure thermal'' closely followed byvacuum’’. Suspicions that the semiclassical calculation of black hole radiance gives evidence for the evolution of pure into mixed states are criticized on this basis. Possible extensions of the model to mimic black holes more accurately (including the effects of back reaction and partial transparency), while remaining within the realm of tractable models, are suggested. |
| Quantum Gravity and Black Hole | Ken-ji Hamada, Asato Tsuchiya | 1993-02-22 | The quantum theory of the spherically symmetric gravity in 3+1 dimensions is investigated. The functional measures are explicitly evaluated and the physical state conditions are derived by using the technique developed in two dimensional quantum gravity. Then the new features which are not seen in ADM formalism come out. If $\kappa_s > 0 $, where $\kappa_s =(N-27)/12\pi $ and $N$ is the number of matter fields, a singularity appears, while for $\kappa_s <0$ the singularity disappears. The quantum dynamics of black hole seems to be changed by the sign of $\kappa_s $. (Talk given by K.H. at Workshop on General Relativity and Gravity, Waseda, Tokyo, Japan, 18-20 Jan 1993.) |
| Do Black Holes Exist? | J. W. Moffat | 1993-02-22 | The problem of information loss in black hole formation and the associated violations of basic laws of physics, such as conservation of energy, causality and unitarity, are avoided in the nonsymmetric gravitational theory, if the NGT charge of a black hole and its mass satisfy an inequality that does not violate any known experimental data and allows the existence of white dwarfs and neutron stars. |
| Charge Quantization of Axion-Dilaton Black Holes | Renata Kallosh, Tomas Ortin | 1993-02-23 | We present axion-dilaton black-hole and multi-black-hole solutions of the low-energy string effective action. Under $SL(2,R)$ electric-magnetic duality rotations only the hair" (charges and asymptotic values of the fields) of our solutions is transformed. The functional form of the solutions is duality-invariant. Axion-dilaton black holes with zero entropy and zero area of the horizon form a family of stable particle-like objects, which we call {\it holons}. We study the quantization of the charges of these objects and its compatibility with duality symmetry. In general the spectrum of black-hole solutions with quantized charges is not invariant under $SL(2,R)$ but only under $SL(2,Z)$ or one of its subgroups $\Gamma_{l}$. Because of their transformation properties, the asymptotic value of the axion-dilaton field of a black hole may be associated with the modular parameter $\tau$ of some complex torus and the integer numbers $(n,m)$ that label its quantized electric and magnetic charges may be associated with winding numbers. |
| [Modeling Complex Nuclear Spectra - Regularity versus Chaos](http://arxiv.org/abs/nucl-th/9302011v1) | S. Drozdz, S. Nishizaki, J. Speth, J. Wambach | 1993-02-24 | A statistical analysis of the spectrum of two particle - two hole doorway states in a finite nucleus is performed. On the unperturbed mean-field level sizable attractive correlations are present in such a spectrum. Including particle-hole rescattering effects via the residual interaction introduces repulsive dynamical correlations which generate the fluctuation properties characteristic of the Gaussian Orthogonal Ensemble. This signals that the underlying dynamics becomes chaotic. This feature turns out to be independent of the detailed form of the residual interaction and hence reflects the generic nature of the fluctuations studied. |
| [Exact Three Dimensional Black Holes in String Theory](http://arxiv.org/abs/hep-th/9302126v1) | Gary T. Horowitz, Dean L. Welch | 1993-02-26 | A black hole solution to three dimensional general relativity with a negative cosmological constant has recently been found. We show that a slight modification of this solution yields an exact solution to string theory. This black hole is equivalent (under duality) to the previously discussed three dimensional black string solution. Since the black string is asymptotically flat and the black hole is asymptotically anti-de Sitter, this suggests that strings are not affected by a negative cosmological constant in three dimensions. |
| [Quantum Black Holes](http://arxiv.org/abs/hep-th/9302127v2) | Juan Garcia-Bellido | 1993-02-26 | Clarified certain points and related it to other work. |
| [Unrecognizable Black Holes in Two Dimensions](http://arxiv.org/abs/hep-th/9302132v1) | T. Fujiwara, Y. Igarashi, J. Kubo | 1993-02-26 | The classical 2D cosmological model of Callan, Giddings, Harvey and Strominger possesses a global symmetry that is responsible for decoupling of matter fields. The model is quantized on the basis of the extended phase space method to allow an exhaustive, algebraic analysis to find potential anomalies. Under a certain set of reasonable assumptions we show that neither the BRST symmetry of the theory nor the global symmetry suffers from an anomaly. From this we conclude that there is nothing to recognize the existence of black hole and therefore nothing to radiate in their cosmological model. |
| [Wave Functional of Quantum Black Holes in Two Dimensions](http://arxiv.org/abs/hep-th/9302142v1) | Takayuki Hori, Masaru Kamata | 1993-02-28 | The wheeler-DeWitt method is applied to the quantization of the 1 + 1 dimensional dilaton gravity coupled with the conformal matter fields. Exact solutions to the WD equations are found, which are interpreted as right(left)-moving black holes. |
| [Two Dimensional Quantum Dilaton Gravity and the Positivity of Energy](http://arxiv.org/abs/hep-th/9302144v2) | S. P. de Alwis | 1993-02-28 | Using an argument due to Regge and Teitelboim, an expression for the ADM mass of 2d quantum dilaton gravity is obtained. By evaluating this expression we establish that the quantum theories which can be written as a Liouville-like theory, have a lower bound to energy, provided there is no critical boundary. This fact is then reconciled with the observation made earlier that the Hawking radiation does not appear to stop. The physical picture that emerges is that of a black hole in a bath of quantum radiation. We also evaluate the ADM mass for the models with RST boundary conditions and find that negative values are allowed. The Bondi mass of these models goes to zero for large retarded times, but becomes negative at intermediate times in a manner that is consistent with the thunderpop of RST. |
| [Super Black Holes](http://arxiv.org/abs/hep-th/9303002v1) | Ulf H. Danielsson | 1993-03-01 | A quantum version of 2D super dilaton gravity containing a black hole is constructed for $N>8$. A previous disagreement as to whether this is possible or not is resolved. |
| [An analytical formula for the vacuum polarization of rotating black
holes](http://arxiv.org/abs/1506.07189v1) | Mirjam Cvetic, Zain H. Saleem, Alejandro Satz | 2015-06-23 | We give an analytical formula for the vacuum polarization of a massless minimally coupled scalar field at the horizon of a rotating black hole with subtracted geometry. This is the first example of an exact, analytical result for a four-dimensional rotating black hole. |
| [Motion and Trajectories of Particles Around Three-Dimensional Black
Holes](http://arxiv.org/abs/gr-qc/9303005v1) | C. Farina, J. Gamboa, A. J. Segui-Santonja | 1993-03-02 | The motion of relativistic particles around three dimensional black holes following the Hamilton-Jacobi formalism is studied. It follows that the Hamilton-Jacobi equation can be separated and reduced to quadratures in analogy with the four dimensional case. It is shown that: a) particles are trapped by the black hole independently of their energy and angular momentum, b) matter alway falls to the centre of the black hole and cannot understake a motion with stables orbits as in four dimensions. For the extreme values of the angular momentum of the black hole, we were able to find exact solutions of the equations of motion and trajectories of a test particle. |
| [General Laws of Black-Hole Dynamics](http://arxiv.org/abs/gr-qc/9303006v3) | Sean A. Hayward | 1993-03-02 | A general definition of a black hole is given, and general `laws of black-hole dynamics' derived. The definition involves something similar to an apparent horizon, a trapping horizon, defined as a hypersurface foliated by marginal surfaces of one of four non-degenerate types, described as future or past, and outer or inner. If the boundary of an inextendible trapped region is suitably regular, then it is a (possibly degenerate) trapping horizon. The future outer trapping horizon provides the definition of a black hole. Outer marginal surfaces have spherical or planar topology. Trapping horizons are null only in the instantaneously stationary case, and otherwise outer trapping horizons are spatial and inner trapping horizons are Lorentzian. Future outer trapping horizons have non-decreasing area form, constant only in the null case---the `second law'. A definition of the trapping gravity of an outer trapping horizon is given, generalizing surface gravity. The total trapping gravity of a compact outer marginal surface has an upper bound, attained if and only if the trapping gravity is constant---the `zeroth law'. The variation of the area form along an outer trapping horizon is determined by the trapping gravity and an energy flux---the `first law'. |
| [Is it possible to recover information from the black-hole radiation?](http://arxiv.org/abs/hep-th/9303011v1) | M. Schiffer | 1993-03-02 | In the framework of communication theory, we analyse the gedanken experiment in which beams of quanta bearing information are flashed towards a black hole. We show that stimulated emission at the horizon provides a correlation between incoming and outgoing radiations consisting of bosons. For fermions, the mechanism responsible for the correlation is the Fermi exclusion principle. Each one of these mechanisms is responsible for the a partial transfer of the information originally coded in the incoming beam to the black--hole radiation. We show that this process is very efficient whenever stimulated emission overpowers spontaneous emission (bosons). Thus, black holes are not `ultimate waste baskets of information'. |
| [Effects of friction on cosmic strings](http://arxiv.org/abs/hep-th/9303024v1) | J. Garriga, M. Sakellariadou | 1993-03-03 | We study the evolution of cosmic strings taking into account the frictional force due to the surrounding radiation. We consider small perturbations on straight strings, oscillation of circular loops and small perturbations on circular loops. For straight strings, friction exponentially suppresses perturbations whose co-moving scale crosses the horizon before cosmological time $t_*\sim \mu^{-2}$ (in Planck units), where $\mu$ is the string tension. Loops with size much smaller than $t_*$ will be approximately circular at the time when they start the relativistic collapse. We investigate the possibility that such loops will form black holes. We find that the number of black holes which are formed through this process is well bellow present observational limits, so this does not give any lower or upper bounds on $\mu$. We also consider the case of straight strings attached to walls and circular holes that can spontaneously nucleate on metastable domain walls. |
| [Dirty black holes: Entropy versus area](http://arxiv.org/abs/hep-th/9303029v2) | Matt Visser | 1993-03-04 | Considerable interest has recently been expressed in the entropy versus area relationship fordirty’’ black holes — black holes in interaction with various classical matter fields, distorted by higher derivative gravity, or infested with various forms of quantum hair. In many cases it is found that the entropy is simply related to the area of the event horizon: S = k A_H/(4\ell_P^2). For example, the entropy = (1/4) area'' law *holds* for: Schwarzschild, Reissner--Nordstrom, Kerr--Newman, and dilatonic black holes. On the other hand, theentropy = (1/4) area’’ law *fails* for: various types of (Riemann)^n gravity, Lovelock gravity, and various versions of quantum hair. The pattern underlying these results is less than clear. This paper systematizes these results by deriving a general formula for the entropy: S = {k A_H/(4\ell_P^2)} + {1/T_H} \int\Sigma rho - {L}E ] K^\mu d\Sigma\mu + \int_\Sigma s V^\mu d\Sigma_\mu. (K^\mu is the timelike Killing vector, V^\mu the four velocity of a co–rotating observer.) If no hair is present the validity of the entropy = (1/4) area'' law reduces to the question of whether or not the Lorentzian energy density for the system under consideration is formally equal to the Euclideanized Lagrangian. ****** To appear in Physical Review D 15 July 1993 ****** [Stylistic changes, minor typos fixed, references updated, discussion of the Born-Infeld system excised] |
| [$O(\tilde d,\tilde d)$ Transformations and 3D Black Hole](http://arxiv.org/abs/hep-th/9303032v1) | Abbas Ali, Alok Kumar | 1993-03-04 | We generalize the results of a previous paper by one of the authors to show a relationship among a class of string solutions through $O(\tilde d, \tilde d)$ transformations. The results are applied to a rotating black hole solution of three dimensional general relativity discussed recently. We extend the black hole solution to string theory and show its connection with the three dimensional black string with nonzero momentum through an $O(\tilde d, \tilde d)$ transformation of the above type. |
| [Microcanonical Action and the Entropy of a Rotating Black Hole](http://arxiv.org/abs/gr-qc/9303012v1) | J. David Brown, James W. York | 1993-03-08 | The authors have recently proposed amicrocanonical functional integral” representation of the density of quantum states of the gravitational field. The phase of this real–time functional integral is determined by a microcanonical" or Jacobi action, the extrema of which are classical solutions at fixed total energy, not at fixed total time interval as in Hamilton's action. This approach is fully general but is especially well suited to gravitating systems because for them the total energy can be fixed simply as a boundary condition on the gravitational field. In this paper we describe how to obtain Jacobi's action for general relativity. We evaluate it for a certain complex metric associated with a rotating black hole and discuss the relation of the result to the density of states and to the entropy of the black hole. (Dedicated to Yvonne Choquet-Bruhat in honor of her retirement.) |
| [Entropy and Area](http://arxiv.org/abs/hep-th/9303048v2) | Mark Srednicki | 1993-03-09 | The ground state density matrix for a massless free field is traced over the degrees of freedom residing inside an imaginary sphere; the resulting entropy is shown to be proportional to the area (and not the volume) of the sphere. Possible connections with the physics of black holes are discussed. |
| [Early Cosmic Formation of Massive Black Holes](http://arxiv.org/abs/astro-ph/9303004v1) | M. Umemura, A. Loeb, E. L. Turner | 1993-03-09 | The evolution of nonlinear density fluctuations around the Jeans mass shortly after cosmological recombination is analyzed using a 3D hydrodynamics/dark--matter code. The Cosmic Background Radiation (CBR) exerts Compton friction on free electrons due to peculiar velocities. The dynamics therefore depends strongly on the gas ionization history. Under a variety of ionization conditions and in systems with or without non-baryonic components, the baryons lose angular momentum efficiently and collapse to form a compact optically--thick object which would probably quickly evolve into a massive black hole. Attention is concentrated on elucidating some of the novel physical effects in early cosmological collapses, but ways in which more realistic calculations might be made and in which the scenario could be incorporated into a more complete cosmogonic model are discussed. |
| [Exact Primordial Black Strings in Four Dimensions](http://arxiv.org/abs/hep-th/9303059v1) | Nemanja Kaloper | 1993-03-10 | A solution of effective string theory in four dimensions is presented which admits interpretation of a rotating black cosmic string. It is constructed by tensoring the three dimensional black hole, extended with the Kalb-Ramond axion, with a flat direction. The physical interpretation of the solution is discussed, with special attention on the axion, which is found to play a role very similar to a Higgs field. Finally, it is pointed out that the solution represents an exact WZWN $\sigma$ model on the string world sheet, to all orders in the inverse string tension $\alpha'$. |
| [Equivalent models for gauged WZW theory](http://arxiv.org/abs/hep-th/9303081v1) | Haruhiko Terao, Kiyonori Yamada | 1993-03-15 | We modify the $SL(2,{\bf R})/U(1)$ WZW theory, which was shown to describe strings in a 2D black hole, to be invariant under chiral $U(1)$ gauge symmetry by introducing a Steukelberg field. We impose several interesting gauge conditions for the chiral $U(1)$ symmetry. In a paticular gauge the theory is found to be reduced to the Liouville theory coupled to the $c=1$ matter perturbed by the so-called black hole mass operator. Also we discuss the physical states in the models briefly. |
| [Binding of holes and pair spectral function in the t-J model](http://arxiv.org/abs/cond-mat/9303029v1) | Didier POILBLANC | 1993-03-17 | Clusters of the two-dimensionnal t--J model with 2 holes and up to 26 sites are diagonalized using a Lanczos algorithm. The behaviour of the binding energy with system size suggests the existence of a finite critical value of J above which binding occurs in the bulk. Only the d-wave pair field operator acting on the Heisenberg GS has a finite overlap with the 2 hole ground state for all the clusters considered. The related spectral function associated with the propagation of a d-wave (spin singlet) pair of holes in the antiferromagnetic background is calculated. The quasiparticle peak at the bottom of the spectrum as well as some structure appearing above the peak survive with increasing cluster size. Although no simple scaling law was found for the quasiparticle weight the data strongly suggest that this weight is finite in the bulk limit and is roughly proportional to the antiferromagnetic coupling J (for J<1). |
| [Dyonic black holes in effective string theories](http://arxiv.org/abs/hep-th/9303102v1) | S. Mignemi | 1993-03-18 | The spherical symmetric dyonic black hole solutions of the effective action of heterotic string are studied perturbatively up to second order in the inverse string tension. An expression for the temperature in term of the mass and the electric and magnetic charge of the black hole is derived and it is shown that its behaviour is qualitatively different in the two special cases where either the electric or the magnetic charge vanishes |
| [Axion-Dilaton Black Holes](http://arxiv.org/abs/hep-th/9303106v1) | Renata Kallosh | 1993-03-19 | In this talk some essential features of stringy black holes are described. We consider charged four-dimensional axion-dilaton black holes. The Hawking temperature and the entropy of all solutions are shown to be simple functions of the squares of supercharges, defining the positivity bounds. Spherically symmetric and multi black hole solutions are presented. The extreme solutions have some unbroken supersymmetries. Axion-dilaton black holes with zero entropy and zero area of the horizon form a family of stable particle-like objects, which we call holons. We discuss the possibility of splitting of nearly extreme black holes into holons. |
| [Matrix Models and Nonperturbative String Propagation in Two-Dimensional
Black Hole Backgrounds](http://arxiv.org/abs/hep-th/9303116v1) | Sumit R. Das | 1993-03-19 | We identify a quantity in the $c=1$ matrix model which describes the wavefunction for physical scattering of a tachyon from a black hole of the two dimensional critical string theory. At the semiclassical level this quantity corresponds to the usual picture of a wave coming in from infinity, part of which enters the black hole becoming singular at the singularity, while the rest is scattered back to infinity, with nothing emerging from the whitehole. We find, however, that the exact nonperturbative wavefunction is nonsingular at the singularity and appears to end up in the asymptotic regionbehind’’ the singularity. |
| [Tachyon Back Reaction on $d = 2$ String Black Hole](http://arxiv.org/abs/hep-th/9303140v2) | S. Kalyana Rama | 1993-03-25 | We describe a static solution for $d = 2$ critical string theory including the tachyon $T$ but with its potential $V (T)$ set to zero. This solution thus incorporates tachyon back reaction and, when $T = 0$, reduces to the black hole solution. When $T \neq 0$ we find that (1) the Schwarzschild horizon of the above black hole splits into two, resembling Reissner-Nordstrom horizons and (2) the curvature scalar develops new singularities at the horizons. We show that these features will persist even when $V (T)$ is nonzero. We present a time dependent extension of our static solution and discuss some possible methods for removing the above singularities. |
| [Energy Momentum Tensor of the Evaporating Black Hole and Local
Bogoljubov Transformations](http://arxiv.org/abs/hep-th/9303147v1) | S. Massar, R. Parentani, R. Brout | 1993-03-26 | The method of Hawking to obtain black hole evaporation through Bogoljubov transformation between asymptotic modes (in and out) is generalized. The construction is local in that the in modes (of say positive frequency) are decomposed by Bogoljubov transformation into positive and negative frequency local inertial modes (i.e. those which are solutions of the d’Alembertian in terms of the local normal coordinates). From this follows an interesting reexpression of the local energy momentum tensor, more particularly of the outgoing energy flux. One finds that even in the local description there exists a partial thermal character parametrized by a local temperature. There exists quantum interference effects as well. These become negligible at large distance from the black hole. |
| [Quasi-Local Gravitational Energy](http://arxiv.org/abs/gr-qc/9303030v1) | Sean A. Hayward | 1993-03-26 | A dynamically preferred quasi-local definition of gravitational energy is given in terms of the Hamiltonian of a 2+2' formulation of general relativity. The energy is well-defined for any compact orientable spatial 2-surface, and depends on the fundamental forms only. The energy is zero for any surface in flat spacetime, and reduces to the Hawking mass in the absence of shear and twist. For asymptotically flat spacetimes, the energy tends to the Bondi mass at null infinity and the \ADM mass at spatial infinity, taking the limit along a foliation parametrised by area radius. The energy is calculated for the Schwarzschild, Reissner-Nordstr\"om and Robertson-Walker solutions, and for plane waves and colliding plane waves. Energy inequalities are discussed, and for static black holes the irreducible mass is obtained on the horizon. Criteria for an adequate definition of quasi-local energy are discussed. |
| [Exotic Black Holes?](http://arxiv.org/abs/gr-qc/9303035v1) | Carl H. Brans | 1993-03-30 | Exotic smooth manifolds, ${\bf R^2\times_\Theta S^2}$, are constructed and discussed as possible space-time models supporting the usual Kruskal presentation of the vacuum Schwarzschild metric locally, but {\em not globally}. While having the same topology as the standard Kruskal model, none of these manifolds is diffeomorphic to standard Kruskal, although under certain conditions some global smooth Lorentz-signature metric can be continued from the local Kruskal form. Consequently, it can be conjectured that such manifolds represent an infinity of physically inequivalent (non-diffeomorphic) space-time models for black holes. However, at present nothing definitive can be said about the continued satisfaction of the Einstein equations. This problem is also discussed in the original Schwarzschild $(t,r)$ coordinates for which the exotic region is contained in a world tube along the time-axis, so that the manifold is spatially, but not temporally, asymptotically standard. In this form, it is tempting to speculate that the confined exotic region might serve as a source for some exterior solution. Certain aspects of the Cauchy problem are also discussed in terms of ${\bf R^4_\\Theta}$\ models which are half-standard'', say for all $t<0,$ but for which $t$ cannot be globally smooth. |
| [4D and 2D Evaporating Dilatonic Black Holes](http://arxiv.org/abs/hep-th/9303170v2) | Yoav Peleg | 1993-03-30 | The picture of S-wave scatering from a 4D extremal dilatonic black hole is examined. Classically, a small matter shock wave will form a non-extremal black hole. In the "throat region" the r-t geometry is exactly that of a collapsing 2D black hole. The 4D Hawking radiation (in this classical background) gives the 2D Hawking radiation exactly in the throat region. Inclusion of the back-reaction changes this picture: the 4D solution can then be matched to the 2D one only if the Hawking radiation is very small and only at the beginning of the radiation. We give that 4D solution. When the total radiating energy approaches the energy carried by the shock wave, the 4D picture breaks down. This happens even before an apparent horizon is formed, which suggests that the 4D semi-classical solution is quite different from the 2D one. |
| [Motion of Inertial Observers Through Negative Energy](http://arxiv.org/abs/gr-qc/9303038v1) | L. H. Ford, Thomas A. Roman | 1993-03-31 | Recent research has indicated that negative energy fluxes due to quantum coherence effects obey uncertainty principle-type inequalities of the form $|\Delta E|\,{\Delta \tau} \lprox 1\,$. Here $|\Delta E|$ is the magnitude of the negative energy which is transmitted on a timescale $\Delta \tau$. Our main focus in this paper is on negative energy fluxes which are produced by the motion of observers through static negative energy regions. We find that although a quantum inequality appears to be satisfied for radially moving geodesic observers in two and four-dimensional black hole spacetimes, an observer orbiting close to a black hole will see a constant negative energy flux. In addition, we show that inertial observers moving slowly through the Casimir vacuum can achieve arbitrarily large violations of the inequality. It seems likely that, in general, these types of negative energy fluxes are not constrained by inequalities on the magnitude and duration of the flux. We construct a model of a non-gravitational stress-energy detector, which is rapidly switched on and off, and discuss the strengths and weaknesses of such a detector. |
| [The Two-Dimensional Stringy Black-Hole: A New Approach and a Pathology](http://arxiv.org/abs/hep-th/9304002v4) | H. J. de Vega, J. Ramírez Mittelbrun, M. Ramón Medrano, N. Sánchez | 1993-04-01 | The string propagation in the two-dimensional stringy black-hole is investigated from a new approach. We completely solve the classical and quantum string dynamics in the lorentzian and euclidean regimes. In the lorentzian case all the physics reduces to a massless scalar particle described by a Klein-Gordon type equation with a singular effective potential. The scattering matrix is found and it reproduces the results obtained by coset CFT techniques. It factorizes into two pieces : an elastic coulombian amplitude and an absorption part. In both parts, an infinite sequence of imaginary poles in the energy appear. The generic features of string propagation in curved D-dimensional backgrounds (string stretching, fall into spacetime singularities) are analyzed in the present case. A new physical phenomenon specific to the present black-hole is found : the quantum renormalization of the speed of light. We find $c_{quantum} = \sqrt}~c_{classical}$, where $k$ is the integer in front of the WZW action. This feature is, however, a pathology. Only for $ k \to \infty$ the pathology disappears (although the conformal anomaly is present). We analyze all the classical euclidean string solutions and exactly compute the quantum partition function. No critical Hagedorn temperature appears here. |
| [From Kaon-Nuclear Interactions to Kaon Condensation](http://arxiv.org/abs/hep-ph/9304204v1) | G. E. Brown, C. -H. Lee, M. Rho, V. Thorsson | 1993-04-02 | An effective chiral Lagrangian in heavy-fermion formalism whose parameters are constrained by kaon-nucleon and kaon-nuclear interactions next to the leading order in chiral expansion is used to describe kaon condensation in dense neutron star" matter. The critical density is found to be robust with respect to the parameters of the chiral Lagrangian and comes out to be $\rho_c\sim (3 - 4)\rho_0$. Once kaon condensation sets in, the system is no longer composed of neutron matter but of nuclear matter. Possible consequences on stellar collapse with the formation of compact nuclear stars" or light-mass black holes are pointed out. |
| [Global Structure of a Black-Hole Cosmos and its Extremes](http://arxiv.org/abs/gr-qc/9304007v1) | Dieter R. Brill, Sean A. Hayward | 1993-04-06 | We analyze the global structure of a family of Einstein-Maxwell solutions parametrized by mass, charge and cosmological constant. In a qualitative classification there are: (i) generic black-hole solutions, describing a Wheeler wormhole in a closed cosmos of spatial topology $S^2\times S^1$; (ii) generic naked-singularity solutions, describing a pair of point" charges in a closed cosmos; (iii) extreme black-hole solutions, describing a pair of horned" particles in an otherwise closed cosmos; (iv) extreme naked-singularity solutions, in which a pair of point charges forms and then evaporates, in a way which is not even weakly censored; and (v) an ultra-extreme solution. We discuss the properties of the solutions and of various coordinate systems, and compare with the Kastor-Traschen multi-black-hole solutions. |
| [Spin-Charge Separation in Two Dimensions - A Numerical Study](http://arxiv.org/abs/cond-mat/9304007v2) | Mihir Arjunwadkar, P. V. Panat, D. G. Kanhere | 1993-04-06 | The question of spin-charge separation in two-dimensional lattices has been addressed by numerical simulations of the motion of one hole in a half-filled band. The calculations have been performed on finite clusters with Hubbard and t-J models. By comparing the time evolution of spin and charge polarisation currents in one and two dimensions, evidence in favor of spin-charge separation in two dimensions is presented. In contrast with this, spin-charge separation is absent in a highly doped, metallic, system. |
| [Matter-ghost mixing and the exact 2d black hole metric](http://arxiv.org/abs/hep-th/9304021v1) | Miao Li | 1993-04-07 | We study a revised version of Witten's 2d black hole, in which the matter and (b,c) ghosts are mixed. The level of the coset model is still 9/4. We show that this model is equivalent to that of Mukhi and Vafa, in which the level of the coset model is taken as 3, and the stress tensor is improved. We argue that the exact metric in such a model is just the semi-classical one, quite different from the exact metric in Witten's black hole, being studied by Dijkgraaf, Verlinde and Verlinde. In addition, there appear ghost-related terms as a part of the background in the world sheet action. |
| [Nilpotent Gauging of SL(2,R)$WZNW$ models, and Liouville Field](http://arxiv.org/abs/hep-th/9304024v2) | M. Alimohammadi, F. Ardalan, H. Arfaei | 1993-04-07 | We consider the gauging of $ SL(2,R) $ WZNW model by its nilpotent subgroup E(1). The resulting space-time of the corresponding sigma model is seen to collapse to a one dimensional field theory of Liouville. Gauging the diagonal subgroup $ E(1) \times U(1) $ of $SL(2,R) \times U(1)$ theory yields an extremal three dimensional black string. We show that these solutions are obtained from the two dimensional black hole of Witten and the three dimensional black string of Horne and Horowitz by boosting the gauge group. |
| [Maximal Hypersurfaces in Asymptotically Stationary Space-Times](http://arxiv.org/abs/gr-qc/9304009v1) | P. T. Chrusciel, R. Wald | 1993-04-07 | Existence of maximal hypersurfaces and of foliations by maximal hypersurfaces is proven in two classes of asymptotically flat spacetimes which possess a one parameter group of isometries whose orbits are timelike near infinity''. The first class consists of strongly causal asymptotically flat spacetimes which contain no black hole or white hole" (but may contain ergoregions" where the Killing orbits fail to be timelike). The second class of spacetimes possess a black hole and a white hole, with the black and white hole horizons intersecting in a compact 2-surface $S$. |
| [Constraints on Black Hole Remnants](http://arxiv.org/abs/hep-th/9304027v3) | S. B. Giddings | 1993-04-07 | One possible fate of information lost to black holes is its preservation in black hole remnants. It is argued that a type of effective field theory describes such remnants (generically referred to as informons). The general structure of such a theory is investigated and the infinite pair production problem is revisited. A toy model for remnants clarifies some of the basic issues; in particular, infinite remnant production is not suppressed simply by the large internal volumes as proposed in cornucopion scenarios. Criteria for avoiding infinite production are stated in terms of couplings in the effective theory. Such instabilities remain a problem barring what would be described in that theory as a strong coupling conspiracy. The relation to euclidean calculations of cornucopion production is sketched, and potential flaws in that analysis are outlined. However, it is quite plausible that pair production of ordinary black holes (e.g. Reissner Nordstrom or others) is suppressed due to strong effective couplings. It also remains an open possibility that a microscopic dynamics can be found yielding an appropriate strongly coupled effective theory of neutral informons without infinite pair production. |
| [The Delta-Hole model at Finite Temperature](http://arxiv.org/abs/nucl-th/9304005v1) | P. A. Henning, H. Umezawa | 1993-04-08 | The spectral function of pions interacting with a gas of nucleons and Delta-33-resonances is investigated using the formalism of Thermo Field Dynamics. After a discussion of the zero Delta-width approximation at finite temperature, we take into account a constant width of the resonance. Apart from a full numerical calculation, we give analytical approximations to the pionic spectral function including such a width. They are found to be different from previous approximations, and require an increase of the effective Delta-width in hot compressed nuclear matter. The results are summarized in an effective dispersion relation for interacting pions. |
| [Towards complete integrability of two dimensional Poincaré gauge
gravity](http://arxiv.org/abs/hep-th/9304043v1) | E. W. Mielke, F. Gronwald, Y. N. Obukhov, R. Tresguerres, F. W. Hehl | 1993-04-10 | It is shown that gravity on the line can be described by the two dimensional (2D) Hilbert-Einstein Lagrangian supplemented by a kinetic term for the coframe and a translational {\it boundary} term. The resulting model is equivalent to a Yang-Mills theory of local {\it translations} and frozen Lorentz gauge degrees. We will show that this restricted Poincar\'e gauge model in 2 dimensions is completely integrable. {\it Exact} wave, charged black hole, and dilaton’ solutions are then readily found. In vacuum, the integrability of the {\it general} 2D Poincar'e gauge theory is formally proved along the same line of reasoning. |
| [Pairing on Small Clusters in the Peierls-Hubbard Model: Implications for
C${60}$](http://arxiv.org/abs/cond-mat/9304022v1) | J. Tinka Gammel F. Guo, D. Guo, K. C. Ung, S. Mazumdar | 1993-04-13 | We study the pairing within the Peierls-Hubbard Model for electron- and hole-doped analogs of C${60}$ accessible to exact diagonalization techniques (cube, truncated tetrahedron, {\it etc.}). We discuss how inclusion of electron-phonon interactions can substantially modify the conclusions about pairing obtained when this coupling is neglected. We also discuss potential pitfalls in the extrapolation from these small system calculations to C${60}$, and stress the necessity of having the correct intuitive picture. |
| [Gravitational Radiation, Inspiraling Binaries, and Cosmology](http://arxiv.org/abs/gr-qc/9304020v1) | David F. Chernoff, Lee Samuel Finn | 1993-04-15 | We show how to measure cosmological parameters using observations of inspiraling binary neutron star or black hole systems in one or more gravitational wave detectors. To illustrate, we focus on the case of fixed mass binary systems observed in a single Laser Interferometer Gravitational-wave Observatory (LIGO)-like detector. Using realistic detector noise estimates, we characterize the rate of detections as a function of a threshold signal-to-noise ratio $\rho_0$, the Hubble constant $H_0$, and the binary chirp'' mass. For $\rho_0 = 8$, $H_0 = 100$ km/s/Mpc, and $1.4 \msun$ neutron star binaries, the sample has a median redshift of $0.22$. Under the same assumptions but independent of $H_0$, a conservative rate density of coalescing binaries ($8\times10^{-8}\,{\rm yr}^{-1}\,{\rm Mpc}^{-3}$) implies LIGO will observe $\sim 50\,{\rm yr}^{-1}$ binary inspiral events. The precision with which $H_0$ and the deceleration parameter $q_0$ may be determined depends on the number of observed inspirals. For fixed mass binary systems, $\sim 100$ observations with $\rho_0 = 10$ in the LIGO detector will give $H_0$ to 10\% in an Einstein-DeSitter cosmology, and 3000 will give $q_0$ to 20\%. For the conservative rate density of coalescing binaries, 100 detections with $\rho_0 = 10$ will require about 4~yrs. |
| [Flat World of Dilatonic Domain Walls](http://arxiv.org/abs/hep-th/9304062v1) | Mirjam Cvetic | 1993-04-16 | We study dilatonic domain walls specific to superstring theory. Along with the matter fields and metric the dilaton also changes its value in the wall background. We found supersymmetric (extreme) solutions which in general interpolate between isolated superstring vacua with non-equal value of the matter potential; they correspond to the static, planar domain walls with {\it flat} metric in the string (sigma model) frame. We point out similarities between the space-time of dilatonic walls and that of charged dilatonic black holes. We also comment on non-extreme solutions corresponding to expanding bubbles. |
| [Relating black holes in two and three dimensions](http://arxiv.org/abs/hep-th/9304068v1) | Ana Achúcarro, Miguel Ortiz | 1993-04-16 | The three dimensional black hole solutions of Ba\~nados, Teitelboim and Zanelli (BTZ) are dimensionally reduced in various different ways. Solutions are obtained to the Jackiw-Teitelboim theory of two dimensional gravity for spinless BTZ black holes, and to a simple extension with a non-zero dilaton potential for black holes of fixed spin. Similar reductions are given for charged black holes. The resulting two dimensional solutions are themselves black holes, and are appropriate for investigating exactS-wave’’ scattering in the BTZ metrics. Using a different dimensional reduction to the string inspired model of two dimensional gravity, the BTZ solutions are related to the familiar two dimensional black hole and the linear dilaton vacuum. |
| [Wave Propagation in Stringy Black Hole](http://arxiv.org/abs/hep-th/9304072v2) | Avinash Dhar, Gautam Mandal, Spenta R. Wadia | 1993-04-17 | We further study the nonperturbative formulation of two-dimensional black holes. We find a nonlinear differential equation satisfied by the tachyon in the black hole background. We show that singularities in the tachyon field configurations are always associated with divergent semiclassical expansions and are absent in the exact theory. We also discuss how the Euclidian black hole emerges from an analytically continued fermion theory that corresponds to the right side up harmonic oscillator potential. |
| [Exiton, Spinon and Spin Wave Modes in an Exactly Soluble One-Dimensional
Quantum Many-Body System](http://arxiv.org/abs/cond-mat/9304033v1) | Bill Sutherland, Rudolf A. R”omer | 1993-04-20 | In this paper, we present the exact solution to a one-dimensional, two-component, quantum many-body system in which like particles interact with a pair potential $s(s+1)/{\rm sinh}^{2}(r)$, while unlike particles interact with a pair potential $-s(s+1)/{\rm cosh}^{2}(r)$. We first give a proof of integrability, then derive the coupled equations determining the complete spectrum. All singularities occur in the ground state when there are equal numbers of the two components; we give explicit results for the ground state and low-lying states in this case. For $s>0$, the system is an antiferromagnet/insulator, with excitations consisting of a pair-hole–pair continuum, a two-particle continuum with gap, and excitons with gaps. For $-1<s<0$, the system has excitations consisting of a hole-particle continuum, and a two-spin wave continuum, both gap-less. |
| [On completeness of orbits of Killing vector fields](http://arxiv.org/abs/gr-qc/9304029v1) | Piotr T. Chrusciel | 1993-04-21 | A Theorem is proved which reduces the problem of completeness of orbits of Killing vector fields in maximal globally hyperbolic, say vacuum, space–times to some properties of the orbits near the Cauchy surface. In particular it is shown that all Killing orbits are complete in maximal developements of asymptotically flat Cauchy data, or of Cauchy data prescribed on a compact manifold. This result gives a significant strengthening of the uniqueness theorems for black holes. |
| [Non-Local Effects in String Black Holes](http://arxiv.org/abs/hep-th/9304105v1) | B. Harms, Y. Leblanc | 1993-04-22 | We consider modifications to general relativity due to non-local string effects by using perturbation theory about the 4-dimensional Schwarzschild black hole metric. In keeping with our interpretation in previous works of black holes as quantum p-branes we investigate non-local effects due to a critical bosonic string compactified down to 4 dimensions. We show that non-local effects do not alter the spacetime topology (at least perturbatively), but they do lead to violations of the area law of black hole thermodynamics and to Hawking’s first law of black hole thermodynamics. We also consider a simple analytic continuation of our perturbaive result into the non-perturbative region, which yields an ultraviolet-finite theory of quantum gravity. The Hawking temperature goes to zero in the non-perturbative region (zero string tension parameter), which is consistent with the view that Planck-size physics is quantum mechanical. |
| [Non-Perturbative 2-Dimensional String Theory](http://arxiv.org/abs/hep-th/9304109v1) | Spenta R. Wadia | 1993-04-23 | We review some aspects of the non-perturbative formulation of 2-dim. string theory in terms of non-relativistic fermions. We derive the bosonization using $W\infty$ coherent states in the path-integral formulation. We discuss the classical limit and indicate the precise nature of the truncation of the full theory that leads to collective field theory. As applications we briefly discuss classical solutions reponsible for stringy non-perturbative effects and the 2-dim. black-hole. |
| [Bound states of holes in an antiferromagnet](http://arxiv.org/abs/cond-mat/9304044v1) | D. Poilblanc, J. Riera, E. Dagotto | 1993-04-26 | The formation of bound states of holes in an antiferromagnetic spin-1/2 background is studied using numerical techniques applied to the ${\rm t-J}$ Hamiltonian on clusters with up to 26 sites. An analysis of the binding energy as a function of cluster size suggests that a two hole bound state is formed for couplings larger than a critical'' value ${\rm J/t]_c}$. The symmetry of the bound state is $\dx2y2$. We also observed that itsquasiparticle’’ weight ${\rm Z_{2h}}$ (defined in the text), is finite for all values of the coupling ${\rm J/t}$. Thus, in the region ${\rm J/t \geq J/t]c}$ the bound state of two holes behaves like a quasiparticle with charge $Q=2e$, spin $S=0$, and $\dx2y2$ internal symmetry. The relation with recent ideas that have suggested the possibility of d-wave pairing in the high temperature cuprate superconductors is briefly discussed. |
| [Quantum Black Hole Evaporation](http://arxiv.org/abs/hep-th/9304128v2) | Kareljan Schoutens, Erik Verlinde, Herman Verlinde | 1993-04-27 | We investigate a recently proposed model for a full quantum description of two-dimensional black hole evaporation, in which a reflecting boundary condition is imposed in the strong coupling region. It is shown that in this model each initial state is mapped to a well-defined asymptotic out-state, provided one performs a certain projection in the gravitational zero mode sector. We find that for an incoming localized energy pulse, the corresponding out-going state contains approximately thermal radiation, in accordance with semi-classical predictions. In addition, our model allows for certain acausal strong coupling effects near the singularity, that give rise to corrections to the Hawking spectrum and restore the coherence of the out-state. To an asymptotic observer these corrections appear to originate from behind the receding apparent horizon and start to influence the out-going state long before the black hole has emitted most of its mass. Finally, by putting the system in a finite box, we are able to derive some algebraic properties of the scattering matrix and prove that the final state contains all initial information. |
| [Numerical Analysis of Black Hole Evaporation](http://arxiv.org/abs/hep-th/9304148v1) | Tsvi Piran, Andrew Strominger | 1993-04-28 | Black hole formation/evaporation in two-dimensional dilaton gravity can be described, in the limit where the number $N$ of matter fields becomes large, by a set of second-order partial differential equations. In this paper we solve these equations numerically. It is shown that, contrary to some previous suggestions, black holes evaporate completely a finite time after formation. A boundary condition is required to evolve the system beyond the naked singularity at the evaporation endpoint. It is argued that this may be naturally chosen so as to restore the system to the vacuum. The analysis also applies to the low-energy scattering of $S$-wave fermions by four-dimensional extremal, magnetic, dilatonic black holes. |
| [ADM masses for black strings and p-branes](http://arxiv.org/abs/hep-th/9304159v2) | J. X. Lu | 1993-04-30 | An ADM mass formula is derived for a wide class of black solutions with certain spherical symmetry. By applying this formula, we calculate the ADM masses for recently discovered black strings and $p$-branes in diverse dimensions. By this, the Bogolmol’nyi equation can be shown to hold explicitly. A useful observation is made for non-extremal black $p$-branes that only for $p = 0$, i.e. for a black hole, can its ADM mass be read directly from the asymptotic behaviour of the metric component $g{00}$. |
| [The spectrum of the 2D Black Hole, or Does the 2D black hole have
tachyonic or W–hair?](http://arxiv.org/abs/hep-th/9305003v1) | Neil Marcus, Yaron Oz | 1993-05-03 | We solve the equations of motion of the tachyon and the discrete states in the background of Witten’s semiclassical black hole and in the exact 2D dilaton-graviton background of Dijkgraaf et al. We find the exact solutions for weak fields, leading to conclusions in disagreement with previous studies of tachyons in the black hole. Demanding that a state in the black hole be well behaved at the horizon implies that it must tend asymptotically to a combination of a Seiberg and an anti-Seiberg c=1 state. For such a state to be well behaved asymptotically, it must satisfy the condition that neither its Seiberg nor its anti-Seiberg Liouville momentum is positive. Thus, although the free-field BRST cohomologies of the underlying SL(2,R)/U(1) theory is the same as that of a c=1 theory, the black hole spectrum is drastically truncated: THERE ARE NO W_INFINITY STATES, AND ONLY TACHYONS WITH X-MOMENTA | P_TACH | <= | M_TACH | ARE ALLOWED. In the Minkowski case only the static tachyon is allowed. The black hole is stable to the back reaction of these remaining tachyons, so they are good perturbations of the black hole, or hair''. However, this leaves only 3 tachyonic hairs in the black hole and 7 in the exact solution! Such sparse hair is clearly irrelevant to the maintenance of coherence during black hole evaporation. |
| [Entropy of Lovelock Black Holes](http://arxiv.org/abs/hep-th/9305016v1) | Ted Jacobson, Robert C. Myers | 1993-05-06 | A general formula for the entropy of stationary black holes in Lovelock gravity theories is obtained by integrating the first law of black hole mechanics, which is derived by Hamiltonian methods. The entropy is not simply one quarter of the surface area of the horizon, but also includes a sum of intrinsic curvature invariants integrated over a cross section of the horizon. |
| [Tachyon Hair on Two-Dimensional Black Holes](http://arxiv.org/abs/hep-th/9305030v1) | A. Peet, L. Susskind, L. Thorlacius | 1993-05-08 | Static black holes in two-dimensional string theory can carry tachyon hair. Configurations which are non-singular at the event horizon have non-vanishing asymptotic energy density. Such solutions can be smoothly extended through the event horizon and have non-vanishing energy flux emerging from the past singularity. Dynamical processes will not change the amount of tachyon hair on a black hole. In particular, there will be no tachyon hair on a black hole formed in gravitational collapse if the initial geometry is the linear dilaton vacuum. There also exist static solutions with finite total energy, which have singular event horizons. Simple dynamical arguments suggest that black holes formed in gravitational collapse will not have tachyon hair of this type. |
| [On the Distributional Nature of the Energy Momentum Tensor of a Black
Hole or What Curves the Schwarzschild Geometry ?](http://arxiv.org/abs/gr-qc/9305009v1) | Herbert Balasin, Herbert Nachbagauer | 1993-05-10 | Using distributional techniques we calculate the energy--momentum tensor of the Schwarzschild geometry. It turns out to be a well--defined tensor--distribution concentrated on the $r=0$ region which is usually excluded from space--time. This provides a physical interpretation for the curvature of this geometry. |
| [Black Hole Information](http://arxiv.org/abs/hep-th/9305040v5) | Don N. Page | 1993-05-10 | Hawking's 1974 calculation of thermal emission from a classical black hole led to his 1976 proposal that information may be lost from our universe as a pure quantum state collapses gravitationally into a black hole, which then evaporates completely into a mixed state of thermal radiation. Another possibility is that the information is not lost, but is stored in a remnant of the evaporating black hole. A third idea is that the information comes out in nonthermal correlations within the Hawking radiation, which would be expected to occur at too slow a rate, or be too spread out, to be revealed by any nonperturbative calculation. |
| [Theory of Photoluminescence from a Magnetic Field Induced
Two-dimensional Quantum Wigner Crystal](http://arxiv.org/abs/cond-mat/9305006v1) | Dong-Zi Liu, H. A. Fertig, S. Das Sarma | 1993-05-11 | We develop a theory of photoluminescence using a time-dependent Hartree-Fock approximation that is appropriate for the two-dimensional Wigner crystal in a strong magnetic field. The cases of localized and itinerant holes are both studied. It is found that the photoluminescence spectrum is a weighted measure of the single particle density of states of the electron system, which for an undisturbed electron lattice has the intricate structure of the Hofstadter butterfly. It is shown that for the case of a localized hole, a strong interaction of the hole with the electron lattice tends to wipe out this structure. In such cases, a single final state is strongly favored in the recombination process, producing a single line in the spectrum. For the case of an itinerant hole, which could be generated in a wide quantum well system, we find that electron-hole interactions do not significantly alter the density of states of the Wigner crystal, opening the possibility of observing the Hofstadter gap spectrum in the electron density of states directly. At experimentally relevant filling fractions, these gaps are found to be extremely small, due to exchange effects. However, it is found that the hole, which interacts with the periodic potential of the electron crystal, has a Hofstadter spectrum with much larger gaps. It is shown that a finite temperature experiment would allow direct probing of this gap structure through photoluminescence. |
| [Abelian and Non-Abelian Dualities in String Bacgrounds](http://arxiv.org/abs/hep-th/9305055v1) | Fernando Quevedo | 1993-05-13 | We present a brief discussion of recent work on duality symmetries in non-trivial string backgrounds. Duality is obtained from a gauged non-linear sigma-model with vanishing gauge field strength. Standard results are reproduced for abelian gauge groups, whereas a new type of duality is identified for non--abelian gauge groups. Examples of duals of WZW models and 4-d black holes are given. (Presented at `From Superstrings to Supergravity', Erice 1992) |
| [Effective Kaon Mass in Baryonic Matter and Kaon Condensation](http://arxiv.org/abs/nucl-th/9305008v1) | Hiroyuki Yabu, Shinji Nakamura, F. Myhrer, K. Kubodera | 1993-05-13 | The effective kaon mass in dense baryonic matter is calculated based on PCAC, current algebra and the Weinberg smoothness hypothesis. The off-shell behavior of the K-N scattering amplitudes is treated consistently with PCAC, and the effects of the subthreshold K-N resonances are also included. The effective kaon mass is found to depend crucially on the K-N sigma term. Since the current estimates of K-N Sigma term are very uncertain, we discuss various scenarios treating K-N Sigma term as an input parameter; for certain values of K-N Sigma a collective mode of a hyperon-particle-nucleon-hole state appears at high densities, possibly leading to kaon condensation. |
| [Quantum Mechanics, Common Sense and the Black Hole Information Paradox](http://arxiv.org/abs/gr-qc/9305012v1) | Ulf H. Danielsson, Marcelo Schiffer | 1993-05-14 | The purpose of this paper is to analyse, in the light of information theory and with the arsenal of (elementary) quantum mechanics (EPR correlations, copying machines, teleportation, mixing produced in sub-systems owing to a trace operation, etc.) the scenarios available on the market to resolve the so-called black-hole information paradox. We shall conclude that the only plausible ones are those where either the unitary evolution of quantum mechanics is given up, in which information leaks continuously in the course of black-hole evaporation through non-local processes, or those in which the world is polluted by an infinite number of meta-stable remnants. |
| [Classical Stringy Black Holes Modify the Thermal Spectrum](http://arxiv.org/abs/hep-th/9305065v1) | B. Harms, Y. Leblanc | 1993-05-14 | Non-local (alpha prime) corrections to Schwarzschild black holes are shown to invalidate the thermodynamical interpretation of black holes. In particular, the canonical and Bekenstein-Hawking temperatures are not equal. The particle number density of fields quantized in the (alpha prime modified) black hole background is no longer thermal. In the non-perturbative region (alpha prime going to infinity or mass going to zero), an analytic continuation to the number density is shown to vanish exponentially. |
| [Effective Action and Exact Geometry in Chiral Gauged WZW Models](http://arxiv.org/abs/hep-th/9305074v3) | Konstadinos Sfetsos | 1993-05-17 | Following recent work on the effective quantum action of gauged WZW models, we suggest such an action for {\it chiral} gauged WZW models which in many respects differ from the usual gauged WZW models. Using the effective action we compute the conformally exact expressions for the metric, the antisymmetric tensor, and the dilaton fields in the $\s$-model arising from a general {\it chiral } gauged WZW model. We also obtain the general solution of the geodesic equations in the exact geometry. Finally we consider in some detail a three dimensional model which has certain similarities with the three dimensional black string model. Finally we consider in some detail a three dimensional model which has certain similarities with the three dimensional black string model. |
| [Do Global String Loops Collapse to Form Black Holes?](http://arxiv.org/abs/hep-th/9305081v1) | Joaquim Fort, Tanmay Vachaspati | 1993-05-18 | Hawking has shown that the emission of gravitational radiation cannot prevent circular loops of gauged cosmic strings from collapsing into black holes. Here we consider the corresponding question for global strings: can Goldstone boson emission prevent circular loops of global cosmic strings from forming black holes? Our results show that for every value of the string tension there is a certain critical size below which the circular loop does not collapse to form a black hole. For GUT scale strings, this critical size is much larger than the current horizon. |
| [Four Dimensional Black Holes in String Theory](http://arxiv.org/abs/hep-th/9305083v1) | S. B. Giddings, J. Polchinski, A. Strominger | 1993-05-19 | Exact solutions of heterotic string theory corresponding to four-dimensional charge Q magnetic black holes are constructed as tensor products of an SU(2)/Z(2Q+2) WZW orbifold with a (0,1) supersymmetric SU(1,1)/U(1) WZW coset model. The spectrum is analyzed in some detail.Bad’’ marginal operators are found which are argued to deform these theories to asymptotically flat black holes. Surprising behaviour is found for small values of Q, where low-energy field theory is inapplicable. At the minimal value Q=1, the theory degenerates. Renormalization group arguments are given that suggest the potential gravitational singularity of the low-energy field theory is resolved by a massive two-dimensional field theory. At Q=0, a stable, neutral remnant,'' of potential relevance to the black hole information paradox, is found. |
| [Dilatonic black holes in theories with moduli fields](http://arxiv.org/abs/hep-th/9305107v1) | M. Cadoni, S. Mignemi | 1993-05-21 | We discuss the low-energy effective string theory when moduli of the compactified manifold are present. Assuming a nontrivial coupling of the moduli to the Maxwell tensor, we find a class of regular black hole solutions. Both the thermodynamical and the geometrical structure of these solutions are discussed |
| [A Deformed Matrix Model and the Black Hole Background in Two-Dimensional
String Theory](http://arxiv.org/abs/hep-th/9305109v3) | Antal Jevicki, Tamiaki Yoneya | 1993-05-21 | The refrerences are corrected. |
| [A Nonsingular Two Dimensional Black Hole](http://arxiv.org/abs/hep-th/9305111v1) | M. Trodden, V. Mukhanov, R. Brandenberger | 1993-05-22 | We construct a model of gravity in 1+1 spacetime dimensions in which the solutions approach the Schwarzschild metric at large $r$ and de Sitter space far inside the horizon. Our model may be viewed as a two dimensional application of the `Limiting Curvature Construction' recently proposed by two of the authors. |
| [Charged Stringy Black Holes With Non-Abelian Hair](http://arxiv.org/abs/hep-th/9305112v1) | E. E. Donets, D. V. Gal'tsov | 1993-05-22 | Static spherically symmetric asymptotically flat charged black hole solutions are constructed within the magnetic SU(3) sector of the 4-dimensional heterotic string effective action. They possess non-abelian hair in addition to the Coulomb magnetic field and are qualitatively similar to the Einstein-Yang-Mills colored SU(3) black holes except for the extremal case. In the extremality limit the horizon shrinks and the resulting geometry around the origin coincides with that of an extremal abelian dilatonic black hole with magnetic charge. Non-abelian hair exibits then typical sphaleron structure. |
| [Anomalous Fermion Production in Gravitational Collapse](http://arxiv.org/abs/gr-qc/9305018v1) | G. W. Gibbons, Alan R. Steif | 1993-05-24 | The Dirac equation is solved in the Einstein-Yang-Mills background found by Bartnik and McKinnon. We find a normalizable zero-energy fermion mode in the $s$-wave sector. As shown recently, their solution corresponds to a gravitational sphaleron which mediates transitions between topologically distinct vacua. Since the Bartnik-McKinnon solution is unstable, it will either collapse to form a black hole or radiate away its energy. In either case, as the Chern-Simons number of the configuration changes, there will be an accompanying anomalous change in fermion number. |
| [A String Derivation of the $\nd{S}$ matrix](http://arxiv.org/abs/hep-th/9305117v1) | J Ellis, N E Mavromatos, D V Nanopoulos | 1993-05-24 | We show that, in string theory, as a result of the $W_{\infty}$-symmetries that preserve quantum coherence in the {\it full} string theory by coupling different mass levels, transitions between initial- and final-state density matrices for the effective light-particle theory involve non-Hamiltonian terms $\nd{\delta H}$ in their time evolution, and are described by a $\nd{S}$ matrix that is not factorizable as a product of field-theoretical $S$ and $S^\dagger$ matrices. We exhibit non-trivial string contributions to $\nd{\delta H}$ and the $\nd{S}$ matrix associated with topological fluctuations related to the coset model that describes an s-wave black hole. These include monopole-antimonopole configurations on the world-sheet that correspond to black hole creation and annihilation, and instantons that represent back-reaction via quantum jumps between black holes of different mass, both of which make the string supercritical. The resulting Liouville mode is interpreted as the time variable, and the arrow of time is associated with black hole decay. Since conformal invariance is broken in the non-critical string theory, monopole and antimonopole, or instanton and anti-instanton, are not separable, and the |
| [Black Holes, Wormholes, and the Disappearance of Global Charge](http://arxiv.org/abs/hep-th/9305123v1) | Sidney Coleman, Shane Hughes | 1993-05-24 | One of the paradoxes associated with the theory of the formation and subsequent Hawking evaporation of a black hole is the disappearance of conserved global charges. It has long been known that metric fluctuations at short distances (wormholes) violate global-charge conservation; if global charges are apparently conserved at ordinary energies, it is only because wormhole-induced global-charge-violating terms in the low-energy effective Lagrangian are suppressed by large mass denominators. However, such suppressed interactions can become important at the high energy densities inside a collapsing star. We analyze this effect for a simple model of the black-hole singularity. (Our analysis is totally independent of any detailed theory of wormhole dynamics; in particular it does not depend on the wormhole theory of the vanishing of the cosmological constant.) We find that in general all charge is extinguished before the infalling matter crosses the singularity. No global charge appears in the outgoing Hawking radiation because it has all gone down the wormholes. |
| [Nonsingular Black Hole Evaporation andStable’’ Remnants | D. A. Lowe, M. O’Loughlin | 1993-05-24 | We examine the evaporation of two–dimensional black holes, the classical space–times of which are extended geometries, like for example the two–dimensional section of the extremal Reissner–Nordstrom black hole. We find that the evaporation in two particular models proceeds to a stable end–point. This should represent the generic behavior of a certain class of two–dimensional dilaton–gravity models. There are two distinct regimes depending on whether the back–reaction is weak or strong in a certain sense. When the back–reaction is weak, evaporation proceeds via an adiabatic evolution, whereas for strong back–reaction, the decay proceeds in a somewhat surprising manner. Although information loss is inevitable in these models at the semi–classical level, it is rather benign, in that the information is stored in another asymptotic region. |
| The First Law of Black Hole Mechanics | Robert M. Wald | 1993-05-25 | A simple proof of a strengthened form of the first law of black hole mechanics is presented. The proof is based directly upon the Hamiltonian formulation of general relativity, and it shows that the the first law variational formula holds for arbitrary nonsingular, asymptotically flat perturbations of a stationary, axisymmetric black hole, not merely for perturbations to other stationary, axisymmetric black holes. As an application of this strengthened form of the first law, we prove that there cannot exist Einstein-Maxwell black holes whose ergoregion is disjoint from the horizon. This closes a gap in the black hole uniqueness theorems. |
| Mass Formulas for Stationary Einstein-Yang-Mills Black Holes and a
Simple Proof of Two Staticity Theorems | Daniel Sudarsky, Robert M. Wald | 1993-05-25 | We derive two new integral mass formulas for stationary black holes in Einstein-Yang-Mills theory. From these we derive a formula for $ \J \Omega -Q V $, from which it follows immediately that any stationary, nonrotating, uncharged black hole is static and has vanishing electric field on the static slices. In the Einstein-Maxwell case, we have, in addition, the generalized Smarr mass formula", for which we provide a new, simple derivation. When combined with the other two formulas, we obtain a simple proof that nonrotating Einstein-Maxwell black holes must be static and have vanishing magnetic field on the static slices. Our mass formulas also can be generalized to cases with other types of matter fields, and we describe the nature of these generalizations. |
| [Sinusoidal Gravitational Waves from the Nuclei of Active Galaxies](http://arxiv.org/abs/astro-ph/9305034v1) | Giacomo Giampieri | 1993-05-26 | It is believed that most quasars and galaxies present two common features: the presence in their core of a supermassive object, and the experience of one or more encounters with other galaxies. In this scenario, it is likely that a substantial fraction of active galactic nuclei harbour a supermassive binary, fueled by an accretion disk. These binaries would certainly be among the strongest sources of sinusoidal gravitational waves. We investigate their evolution considering, simultaneously, the accretion of the black hole's masses from the disk, and the gravitational waves emitted during the orbital motion. We also consider other astrophysical scenarios involving a coalescing binary with non constant masses. |
| [Motion of a Solar Mass Compact Object Around a Massive Rotating Black
Hole](http://arxiv.org/abs/astro-ph/9305035v1) | V. Karas, D. Vokrouhlicky | 1993-05-27 | This preprint is based on two articles accepted by MNRAS and ApJ. Our aim is to study the evolution of the orbit of a star under the influence of interactions with an accretion disc in an AGN. The model considered consists of a low-mass compact object orbiting a supermassive black hole and colliding periodically with the accretion disc. Gravitational field of the nucleus is described by the Kerr metric. The star is assumed to move along a geodesic arc between successive interactions with an equatorial accretion disc. We study the gravitomagnetic (Lense-Thirring) precession of the trajectory. We do not assume any particular value for the eccentricity or inclination of the orbit or the angular momentum of the black hole. We also discuss the periodicity related to the relativistic shift of the pericenter. The model of star-disc interactions has been suggested to explain the X-ray variability observed in the Seyfert galaxy NGC~6814. We briefly discuss on this subject. |
| [Quantum Coherence in Two Dimensions](http://arxiv.org/abs/hep-th/9305165v2) | S. W. Hawking, J. D. Hayward | 1993-05-28 | The formation and evaporation of two dimensional black holes are discussed. It is shown that if the radiation in minimal scalars has positive energy, there must be a global event horizon or a naked singularity. The former would imply loss of quantum coherence while the latter would lead to an even worse breakdown of predictability. CPT invariance would suggest that there ought to be past horizons as well. A way in which this could happen with wormholes is described. |
| [BRST Analysis of Physical States in Two-Dimensional Black Hole](http://arxiv.org/abs/hep-th/9305179v1) | Katsumi Itoh, Hiroshi Kunitomo, Nobuyoshi Ohta, Makoto Sakaguchi | 1993-05-31 | We study the BRST cohomology for $SL(2,R)/U(1)$ coset model, which describes an exact string black hole solution. It is shown that the physical spectrum could contain not only the extra discrete states corresponding to those in $c=1$ two-dimensional gravity but also many additional new states with ghost number $N_{FP}= -1 \sim 2$. We also discuss characters for nonunitary representations and the relation of our results to other approaches. |
| [Toward a Unified Magnetic Phase Diagram of the Cuprate Superconductors](http://arxiv.org/abs/cond-mat/9306007v1) | A. Sokol, D. Pines | 1993-06-02 | We propose a unified magnetic phase diagram of cuprate superconductors. A new feature of this phase diagram is a broad intermediate doping region of quantum-critical, $z=1$, behavior, characterized by temperature independent $T_1T/T_{\rm 2G}$ and linear $T_1T$, where the spin waves are not completely absorbed by the electron-hole continuum. The spin gap in the moderately doped materials is related to the suppression of the low-energy spectral weight in the quantum disordered, $z=1$, regime. The crossover to the $z=2$ regime, where $T_1T/T_{\rm 2G}^2 \simeq \mbox{const}$, occurs only in the fully doped materials. |
| [Ordinary and Dilatonic Domain Walls: Solutions and Induced Space-Times](http://arxiv.org/abs/hep-th/9306015v1) | Mirjam Cvetic | 1993-06-02 | Recent developments in unifying treatment of domain wall configurations and their global space-time structure is presented. Domain walls between vacua of non-equal cosmological constant fall in three classes depending on the value of their energy density $\sigma$: (i) extreme walls with $\sigma=\sigma_{ext}$ are planar, static walls corresponding to the supersymmetric configurations, (ii) non-extreme walls with $\sigma>\sigma_{ext}$ are expanding bubbles with two insides, (iii) ultra-extreme walls with $\sigma<\sigma_{ext}$ are bubbles of false vacuum decay. As a prototype exhibiting all three types of configurations vacuum walls between Minkowski and anti-deSitter vacua are discussed. Space-times associated with these walls exhibit non-trivial causal structure closely related to the one of the corresponding extreme and non-extreme charged black holes, however, without singularities. Recently discovered extreme dilatonic walls, pertinent to string theory, are also addressed. They are static, planar domain walls with metric in the string frame being {\it flat} everywhere. Intriguing similarities between the global space-time of dilatonic walls and that of charged dilatonic black holes are pointed out. |
| [Constraints on Cosmic Strings due to Black Holes Formed from Collapsed
Cosmic String Loops](http://arxiv.org/abs/hep-ph/9306221v1) | R. R. Caldwell, E. Gates | 1993-06-03 | The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict $f$, the fraction of cosmic string loops which collapse to form black holes, and $\mu$, the cosmic string mass-per-unit-length. Using a realistic model of cosmic strings, we find the strongest restriction on the parameters $f$ and $\mu$ is due to the energy density in $100 MeV$ photons radiated by the black holes. We also find that inert black hole remnants cannot serve as the dark matter. If earlier, crude estimates of $f$ are reliable, our results severely restrict $\mu$, and therefore limit the viability of the cosmic string large-scale structure scenario. |
| [Black Holes and Quantum Predictability](http://arxiv.org/abs/hep-th/9306041v2) | S. B. Giddings | 1993-06-08 | A brief review of the confrontation between black hole physics and quantum-mechanical unitarity is presented. Possibile reconciliations are modifying the laws of physics to allow fundamental loss of information, escape of information during the Hawking process, or black hole remnants. Each of these faces serious objections. A better understanding of the problem and its possible solutions can be had by studying two-dimensional models of dilaton gravity. Recent developments in these investigations are summarized. (Linear superposition of talks presented at the 7th Nishinomiya Yukawa Memorial Symposium and at the 1992 YITP Workshop on Quantum Gravity, November 1992.) |
| [Excitation spectrum and critical exponents of a one-dimensional
integrable model of fermions with correlated hopping](http://arxiv.org/abs/cond-mat/9306018v1) | R. Z. Bariev, A. Klümper, A. Schadschneider, J. Zittartz | 1993-06-08 | We investigate the excitation spectrum of a model of $N$ colour fermions with correlated hopping which can be solved by a nested Bethe ansatz. The gapless excitations of particle-hole type are calculated as well as the spin-wave like excitations which have a gap. Using general predictions of conformal field theory the long distance behaviour of some groundstate correlation functions are derived from a finite-size analysis of the gapless excitations. From the algebraic decay we show that for increasing particle density the correlation of so-called $N$-multiplets of particles dominates over the density-density correlation. This indicates the presence of bound complexes of these $N$-multiplets. This picture is also supported by the calculation of the effective mass of charge carriers. |
| [An Upper Limit to the Mass of Black Holes in the Halo of our Galaxy](http://arxiv.org/abs/astro-ph/9306004v1) | Ben Moore | 1993-06-10 | If massive black holes constitute the dark matter in the halo surrounding the Milky Way, the existence of low mass globular clusters in the halo suggests an upper limit to their mass, $M_{_{BH}}$. We use a combination of the impulse approximation and numerical simulations to constrain $M_{_{BH}} \lsim 10^3M_\odot$, otherwise several of the halo globular clusters would be heated to disruption within one half of their lifetime. Taken at face value, this constraint is three orders of magnitude stronger than the previous limit provided by disk heating arguments. However, since the initial mass function of clusters is unknown, we argue that the real constraint is at most, an order of magnitude weaker. Our results rule out cosmological scenarios, such as versions of the Primordial Baryonic Isocurvature fluctuation model, which invoke the low Jeans mass at early epochs to create a large population of black holes of mass $\sim 10^6M_\odot$. |
| [On the Internal Structure of the Singlet d$_{X^2-Y^2}$ Hole Pair in an
Antiferromagnet](http://arxiv.org/abs/cond-mat/9306030v1) | Didier Poilblanc | 1993-06-10 | Exact diagonalizations of two dimensional small t--J clusters reveal dominant hole-hole correlations at distance $\sqrt{2}$ (ie between holes on next nearest neighbor sites). A new form of singlet $d_{x^2-y^2}$ pair operator is proposed to account for the spatial extention of the two hole-bound pair beyond nearest neighbor sites. |
| [The Fourth Law of Black Hole Thermodynamics](http://arxiv.org/abs/gr-qc/9306014v1) | C. O. Lousto | 1993-06-10 | We show that black holes fulfill the scaling laws arising in critical transitions. In particular, we find that in the transition from negative to positive values the heat capacities $C_{JQ}$, $C_{\Omega Q}$ and $C_{J\Phi}$ give rise to critical exponents satisfying the scaling laws. The three transitions have the same critical exponents as predicted by the universality Hypothesis. We also briefly discuss the implications of this result with regards to the connections among gravitation, quantum mechanics and statistical physics. |
| [Black and super p-branes in diverse dimensions](http://arxiv.org/abs/hep-th/9306052v1) | M. J. Duff, J. X. Lu | 1993-06-10 | We present a generic Lagrangian, in arbitrary spacetime dimension $D$, describing the interaction of a dilaton, a graviton and an antisymmetric tensor of arbitrary rank $d$. For each $D$~and~$d$, we findsolitonic’’ black $\tilde{p}$-brane solutions where $\tilde{p} = \tilde{d} - 1$~and~ $\tilde d = D - d - 2$. These solutions display a spacetime singularity surrounded by an event horizon, and are characterized by a mass per unit $\tilde p$-volume, ${\cal M}{\tilde{d}}$, and topological magnetic'' charge $g_{\tilde{d}}$, obeying $\kappa {\cal M}_{\tilde{d}} \geq g_{\tilde{d}}/ \sqrt{2}$. In the extreme limit $\kappa {\cal M}_{\tilde{d}}=g_{\tilde{d}}/ \sqrt{2}$, the singularity and event horizon coalesce. For specific values of $D$~and~$d$, these extreme solutions also exhibit supersymmetry and may be identified with previously classified heterotic, Type IIA and Type IIB super $\tilde p$-branes. The theory also admits elementary $p$-brane solutions withelectric’’ Noether charge $e_d$, obeying the Dirac quantization rule $e_d g{\tilde{d}} = 2\pi n$, $n =$~integer. We also present the Lagrangian describing the theory dual to the original theory, whose antisymmetric tensor has rank $\tilde{d}$ and for which the roles of topological and elementary solutions are interchanged. The super $p$-branes and their duals are mutually non-singular. As special cases of our general solution we recover the black $p$-branes of Horowitz and Strominger $(D = 10)$, Guven $(D = 11)$ and Gibbons et al $(D = 4)$, the $N = 1$, $N = 2a$~and~$N = 2b$ super-$p$-branes of Dabholkar et al $(4 \leq D \leq 10)$, Duff and Stelle $(D = 11)$, Duff and Lu $(D = 10)$ and Callan, Harvey and Strominger $(D = 10)$, and the axionic instanton of Rey $(D = 4)$. In particular, the electric/magnetic duality of Gibbons and Perry in $D = 4$ is seen to be a consequence of particle/sixbrane duality in $D = 10$. Among the new solutions is a self-dual superstring in $D = 6$. |
| The Stretched Horizon and Black Hole Complementarity | L. Susskind, L. Thorlacius, J. Uglum | 1993-06-16 | Three postulates asserting the validity of conventional quantum theory, semi-classical general relativity and the statistical basis for thermodynamics are introduced as a foundation for the study of black hole evolution. We explain how these postulates may be implemented in a stretched horizon'' or membrane description of the black hole, appropriate to a distant observer. The technical analysis is illustrated in the simplified context of 1+1 dimensional dilaton gravity. Our postulates imply that the dissipative properties of the stretched horizon arise from a course graining of microphysical degrees of freedom that the horizon must possess. A principle of black hole complementarity is advocated. The overall viewpoint is similar to that pioneered by 't~Hooft but the detailed implementation is different. |
| [The No-Hair Conjecture in 2D Dilaton Supergravity](http://arxiv.org/abs/gr-qc/9306022v1) | J. Gamboa, Y. Georgelin | 1993-06-17 | We study two dimensional dilaton gravity and supergravity following hamiltonian methods. Firstly, we consider the structure of constraints of 2D dilaton gravity and then the 2D dilaton supergravity is obtained taking the squere root of the bosonic constraints. We integrate exactly the equations of motion in both cases and we show that the solutions of the equation of motion of 2D dilaton supergravity differs from the solutions of 2D dilaton gravity only by boundary conditions on the fermionic variables, i.e. the black holes of 2D dilaton supergravity theory are exactly the same black holes of 2D bosonic dilaton gravity modulo supersymmetry transformations. This result is the bidimensional analogue of the no-hair theorem for supergravity. |
| [Entropy in Black Hole Pair Production](http://arxiv.org/abs/gr-qc/9306023v1) | D. Garfinkle, S. B. Giddings, A. Strominger | 1993-06-18 | Pair production of Reissner-Nordstrom black holes in a magnetic field can be described by a euclidean instanton. It is shown that the instanton amplitude contains an explicit factor of $e^{A/4}$, where $A$ is the area of the event horizon. This is consistent with the hypothesis that $e^{A/4}$ measures the number of black hole states. |
| [Information in Black Hole Radiation](http://arxiv.org/abs/hep-th/9306083v2) | Don N. Page | 1993-06-18 | If black hole formation and evaporation can be described by an $S$ matrix, information would be expected to come out in black hole radiation. An estimate shows that it may come out initially so slowly, or else be so spread out, that it would never show up in an analysis perturbative in $M_{Planck}/M$, or in 1/N for two-dimensional dilatonic black holes with a large number $N$ of minimally coupled scalar fields. |
| [Killing Spinor Identities](http://arxiv.org/abs/hep-th/9306085v1) | Renata Kallosh, Tomas Ortin | 1993-06-18 | We have found generic Killing spinor identities which bosonic equations of motion have to satisfy in supersymmetric theories if the solutions admit Killing spinors. Those identities constrain possible quantum corrections to bosonic solutions with unbroken supersymmetries. As an application we show that purely electric static extreme dilaton black holes may acquire specific quantum corrections, but the purely magnetic ones cannot. |
| [A Self-Consistent Model For The Long-Term Gamma-Ray Spectral Variability
of Cygnus X-1](http://arxiv.org/abs/astro-ph/9306017v1) | Fulvio Melia, Ranjeev Misra | 1993-06-19 | The long-term transitions of the black hole candidate Cygnus X-1 (between the states gamma_1, gamma_2, and gamma_3) include the occasional appearance of a strong ~ MeV bump (gamma_1), whose strength appears to be anti-correlated with the continuum flux (~ 400 keV) due to the Compton upscattering of cold disk photons by the inner, hot corona. We develop a self-consistent disk picture that accounts naturally for these transitions and their corresponding spectral variations. We argue that the bump is due to the self-Comptonization of bremsstrahlung photons emitted predominantly near the plane of the corona itself. Our results suggest that a decrease by a factor of approx 2 in the viscosity parameter alpha is responsible for quenching this bump and driving the system to the gamma_2 state, whereas a transition from gamma_2 to gamma_3 appears to be induced by an increase of about 25 % in the accretion rate Mdot. In view of the fact that most of the transitions observed in this source seem to be of the gamma_2 to gamma_3 variety, we conclude that much of the long term gamma-ray spectral variability in Cygnus X-1 is due to these small fluctuations in Mdot. The unusual appearance of the gamma_1 state apparently reflects a change in the dissipative processes within the disk. |
| [Critical Point Field Mixing in an Asymmetric Lattice Gas Model](http://arxiv.org/abs/cond-mat/9306042v1) | N. B. Wilding | 1993-06-19 | The field mixing that manifests broken particle-hole symmetry is studied for a 2-D asymmetric lattice gas model having tunable field mixing properties. Monte Carlo simulations within the grand canonical ensemble are used to obtain the critical density distribution for different degrees of particle-hole asymmetry. Except in the special case when this asymmetry vanishes, the density distributions exhibit an antisymmetric correction to the limiting scale-invariant form. The presence of this correction reflects the mixing of the critical energy density into the ordering operator. Its functional form is found to be in excellent agreement with that predicted by the mixed-field finite-size-scaling theory of Bruce and Wilding. A computational procedure for measuring the significant field mixing parameter is also described, and its accuracy gauged by comparing the results with exact values obtained analytically. |
| [Supersymmetry and Black Holes](http://arxiv.org/abs/hep-th/9306095v2) | Renata Kallosh | 1993-06-20 | We consider static black holes, which are bosonic solutions of supersymmetric theories. We will show that supersymmetry provides a natural framework for a discussion of various properties of such static black holes. The most fundamental property of simple global supersymmetry, non-negativeness of the energy, is generalized in the black hole theory to cosmic censorship. The SUSY classification of static black holes will be presented in terms of central charges of supersymmetry algebra. The mass, the temperature and the entropy of these black holes are simple functions of supersymmetry charges. The extreme black holes have zero temperature and some unbroken supersymmetries. |
| [Black Hole Physics from Two Dimensional Dilaton Gravity based on
$SL(2,R)/U(1)$ Coset Model](http://arxiv.org/abs/hep-th/9306097v1) | Shin'ich Nojiri, Ichiro Oda | 1993-06-21 | We analyze quantum two dimensional dilaton gravity model, which is described by $SL(2,R)/U(1)$ gauged Wess-Zumino-Witten model deformed by $(1,1)$ operator. We show that the curvature singularity does not appear when the central charge $c_{\rm matter}$ of the matter fields is given by $22<c_{\rm matter}<24$. When $22<c_{\rm matter}<24$, the matter shock waves, whose energy momentum tensors are given by $T_{\rm matter} \propto \delta(x^+ - x^+_0)$, create a kind of wormholes, {\it i.e.,} causally disconnected regions. Most of the quantum informations in past null infinity are lost in future null infinity but the lost informations would be carried by the wormholes. We also discuss about the problem of defining the mass of quantum black holes. On the basis of the argument by Regge and Teitelboim, we show that the ADM mass measured by the observer who lives in one of asymptotically flat regions is finite and does not vanish in general. On the other hand, the Bondi mass is ill-defined in this model. Instead of the Bondi mass, we consider the mass measured by observers who live in an asymptotically flat region at first. A class of the observers finds the mass of the black hole created by a shock wave changes as the observers' proper time goes by, i.e. they observe the Hawking radiation. The measured mass vanishes after the infinite proper time and the black hole evaporates completely. Therefore the total Hawking radiation is positive even when $N<24$. |
| [Weakly Damped Modes in Star Clusters and Galaxies](http://arxiv.org/abs/astro-ph/9306020v1) | Martin D. Weinberg | 1993-06-22 | A perturber may excite a coherent mode in a star cluster or galaxy. If the stellar system is stable, it is commonly assumed that such a mode will be strongly damped and therefore of little practical consequence other than redistributing momentum and energy deposited by the perturber. This paper demonstrates that this assumption is false; weakly damped modes exist and may persist long enough to have observable consequences. To do this, a method for investigating the dispersion relation for spherical stellar systems and for locating weakly damped modes in particular is developed and applied to King models of varying concentration. This leads to the following remarkable result: King models exhibit {\it very} weakly damped $m=1$ modes over a wide range of concentration ($0.67\le c\le1.5$ have been examined). The predicted damping time is tens to hundreds of crossing times. This mode causes the peak density to shift from and slowly revolve about the initial center. The existence of the mode is supported by n-body simulation. Higher order modes and possible astronomical consequences are discussed. Weakly damped modes, for example, may provide a natural explanation for observed discrepancies between density and kinematic centers in galaxies, the location of velocity cusps due to massive black holes, and $m=1$ disturbances of disks embedded in massive halos. Gravitational shocking may excite the $m=1$ mode in globular clusters, which could modify their subsequent evolution and displace the positions of exotic remnants. |
| [Black Hole with Non-Commutative Hair](http://arxiv.org/abs/gr-qc/9306032v1) | C. Klimcik, P. Kolnik, A. Pompos | 1993-06-25 | The specific nonlinear vector $\sigma$-model coupled to Einstein gravity is investigated. The model arises in the studies of the gravitating matter in non-commutative geometry. The static spherically symmetric spacetimes are identified by direct solving of the field equations. The asymptotically flat black hole with thenon-commutative’’ vector hair appears for the special choice of the integration constants, giving thus another counterexample to the famous no-hair'' theorem. |
| [States and quantum effects in the collective field theory of a deformed
matrix model](http://arxiv.org/abs/hep-th/9306141v1) | Kresimir Demeterfi, Joao P. Rodrigues | 1993-06-27 | We derive an equation which gives the tree-level scattering amplitudes for tachyons in the black hole background using the exact states of the collective field hamiltonian corresponding to a deformed matrix model recently proposed by Jevicki and Yoneya. Using directly the symmetry algebra we obtain explicit expression for a class of amplitudes in the tree approximation. We also study the quantum effects in the corresponding collective field theory. In particular, we compute the ground state energy and the free energy at finite temperature up to two loops, and the first quantum correction to the two-point function. |
| [Bosonization of Fermi liquids](http://arxiv.org/abs/cond-mat/9307005v1) | A. H. Castro Neto, Eduardo Fradkin | 1993-07-02 | We bosonize a Fermi liquid in any number of dimensions in the limit of long wavelengths. From the bosons we construct a set of coherent states which are related with the displacement of the Fermi surface due to particle-hole excitations. We show that an interacting hamiltonian in terms of the original fermions is quadratic in the bosons. We obtain a path integral representation for the generating functional which in real time, in the semiclassical limit, gives the Landau equation for sound waves and in the imaginary time gives us the correct form of the specific heat for a Fermi liquid even with the corrections due to the interactions between the fermions. We also discuss the similarities between our results and the physics of quantum crystals. |
| [Conjectures on Non-Local Effects in String Black Holes](http://arxiv.org/abs/hep-th/9307042v1) | B. Harms, Y. Leblanc | 1993-07-06 | We consider modifications to general relativity by the non-local (classical and quantum) string effects for the case of a D-dimensional Scwarzschild black hole. The classical non-local effects do not alter the spacetime topology (the horizon remains unshifted, at least perturbatively). We suggest a simple analytic continuation of the perturbative result into the non-perturbative domain, which eliminates the black hole singularity at the origin and yields an ultraviolet-finite theory of quantum gravity. We investigate the quantum non- local effects (including massive modes) and argue that the inclusion of these back reactions resolves the problem of the thermal spectrum in the semi- classical approach of field quantization in a black hole background, through the bootstrap condition. The density of states for both the quantum and thermal interpretation of the WKB formula are finally shown to differ quant- itatively when including the non-local effects. |
| [Conformal Invariance of Black Hole Temperature](http://arxiv.org/abs/gr-qc/9307002v1) | Ted Jacobson, Gungwon Kang | 1993-07-06 | It is shown that the surface gravity and temperature of a stationary black hole are invariant under conformal transformations of the metric that are the identity at infinity. More precisely, we find a conformal invariant definition of the surface gravity of a conformal Killing horizon that agrees with the usual definition(s) for a true Killing horizon and is proportional to the temperature as defined by Hawking radiation. This result is reconciled with the intimate relation between the trace anomaly and the Hawking effect, despite the {\it non}invariance of the trace anomaly under conformal transformations. |
| [Quantum Dust Black Holes](http://arxiv.org/abs/hep-th/9307057v1) | Yoav Peleg | 1993-07-08 | By analysing the infinite dimensional midisuperspace of spherically symmetric dust universes, and aply it to collapsing dust stars, one finds that the general quantum state is a bound state. This leads to discrete spectrum. In the case of a Schwarzschild black hole, the discrete spectrum implies Bekenstein area quantization: the area of the horizon is an integer multiple of the Planck area. Knowing the microscopic (quantum) states, we suggest a microscopic interpretation of the thermodynamics of black holes: the degeneracy of the quantum states forming a black hole, gives the Bekenstein- Hawking entropy. All other thermodynamical quantities can be derived by using the standard definitions. |
| [Black Hole Statistics](http://arxiv.org/abs/hep-th/9307059v1) | Andrew Strominger | 1993-07-09 | The quantum statistics of charged, extremal black holes is investigated beginning with the hypothesis that the quantum state is a functional on the space of closed three-geometries, with each black hole connected to an oppositely charged black hole through a spatial wormhole. From this starting point a simple argument is given that a collection of extremal black holes obeys neither Bose nor Fermi statistics. Rather they obey an exotic variety of particle statistics known asinfinite statistics’’ which resembles that of distinguishable particles and is realized by a $q$-deformation of the quantum commutation relations. |
| 2D dilaton-gravity from 5D Einstein equations | P. F. González-Díaz | 1993-07-09 | A semiclassical two-dimensional dilaton-gravity model is obtained by dimensional reduction of the spherically symmetric five-dimensional Einstein equations and used to investigate black hole evaporation. It is shown that this model prevents the formation of naked singularity and allows spacetime wormholes to contribute the process of formation and evaporation of black holes. |
| Quantum Evaporation of Liouville Black Holes | R. B. Mann | 1993-07-09 | The classical field equations of a Liouville field coupled to gravity in two spacetime dimensions are shown to have black hole solutions. Exact solutions are also obtained when quantum corrections due to back reaction effects are included, modifying both the ADM mass and the black hole entropy. The thermodynamic limit breaks down before evaporation of the black hole is complete, indicating that higher-loop effects must be included for a full description of the process. A scenario for the final state of the black hole spacetime is suggested. |
| White Holes, Black Holes and Cpt in Two Dimensions | Andrew Strominger | 1993-07-11 | It is argued that a unitarity-violating but weakly CPT invariant superscattering matrix exists for leading-order large-$N$ dilaton gravity, if and only if one includes in the Hilbert space planckian ``thunderpop” excitations which create white holes. CPT apparently cannot be realized in a low-energy effective theory in which such states have been integrated out. Rules for computing the leading-large-$N$ superscattering are described in terms of quantum field theory on a single multiply-connected spacetime obtained by sewing the future (past) horizons of the original spacetime with the past (future) horizons of its CPT conjugate. Some difficulties which may arise in going beyond leading order in $1/N$ are briefly discussed. |
| Beyond the black disk limit | S. M. Troshin, N. E. Tyurin | 1993-07-12 | We consider consequences of violation of the black disk limit possibly revealed by the new CDF measurements of the total, elastic and diffractive cross–sections. |
| Testing Cosmic Censorship with Black Hole Collisions | Dieter Brill, Gary Horowitz, David Kastor, Jennie Traschen | 1993-07-12 | There exists an upper limit on the mass of black holes when the cosmological constant $\Lambda$ is positive. We study the collision of two black holes whose total mass exceeds this limit. Our investigation is based on a recently discovered exact solution describing the collision of $Q=M$ black holes with $\Lambda > 0$. The global structure of this solution is analyzed. We find that if the total mass is less than the extremal limit, then the black holes coalesce. If it is greater, then a naked singularity forms to the future of a Cauchy horizon. However, the horizon is not smooth. Generically, there is a mild curvature singularity, which still allows geodesics to be extended. The implications of these results for cosmic censorship are discussed. |
| Critical Exponents for the SC-Model in the Zero Sector | Rudolf A. Römer, Bill Sutherland | 1993-07-12 | In this paper, we continue our investigation of a one-dimensional, two-component, quantum many-body system in which like particles interact with a pair potential $s(s+1)/{\rm sinh}^{2}(r)$, while unlike particles interact with a pair potential $-s(s+1)/{\rm cosh}^{2}(r)$. For an equal number of particles of the two components, the ground state for $s>0$ corresponds to an antiferromagnet/insulator. Excitations consist of a gapless pair-hole–pair continuum, a two-particle continuum with gap and excitons with gap. For $-1<s<0$, the system has two gapless excitations — a particle-hole continuum and a two spin-wave continuum. Using finite-size scaling methods of conformal field theory, we calculate the asymptotic expressions and critical exponents for correlation functions of these gapless excitations at zero temperature. The conformal structure is closely related to the Hubbard model with repulsive on-site interaction. |
| Generalized Sums over Histories for Quantum Gravity I. Smooth Conifolds | Kristin Schleich, Donald M. Witt | 1993-07-13 | This paper proposes to generalize the histories included in Euclidean functional integrals from manifolds to a more general set of compact topological spaces. This new set of spaces, called conifolds, includes nonmanifold stationary points that arise naturally in a semiclasssical evaluation of such integrals; additionally, it can be proven that sequences of approximately Einstein manifolds and sequences of approximately Einstein conifolds both converge to Einstein conifolds. Consequently, generalized Euclidean functional integrals based on these conifold histories yield semiclassical amplitudes for sequences of both manifold and conifold histories that approach a stationary point of the Einstein action. Therefore sums over conifold histories provide a useful and self-consistent starting point for further study of topological effects in quantum gravity. Postscript figures available via anonymous ftp at black-hole.physics.ubc.ca (137.82.43.40) in file gen1.ps. |
| Complete Semiclassical Treatment of the Quantum Black Hole Problem | B. Harms, Y. Leblanc | 1993-07-15 | Two types of semiclassical calculations have been used to study quantum effects in black hole backgrounds, the WKB and the mean field approaches. In this work we systematically reconstruct the logical implications of both methods on quantum black hole physics and provide the link between these two approaches. Our conclusions completely support our previous findings based solely on the WKB method: quantum black holes are effectively p-brane excitations and, consequently, no information loss paradox exists in this problem. |
| Ultraviolet and soft X–ray photon–photon elastic scattering in an
electron gas | R. Martoňák, E. Tosatti | 1993-07-17 | We have considered the processes which lead to elastic scattering between two far ultraviolet or X–ray photons while they propagate inside a solid, modeled as a simple electron gas. The new ingredient, with respect to the standard theory of photon–photon scattering in vacuum, is the presence of low–energy, nonrelativistic electron–hole excitations. Owing to the existence of two–photon vertices, the scattering processes in the metal are predominantly of second order, as opposed to fourth order for the vacuum case. The main processes in second order are dominated by exchange of virtual plasmons between the two photons. For two photons of similar energy $\hbar \Omega$, this gives rise to a cross section rising like $\Omega^2$ up to maximum of around $10^{-32}$~cm$^2$, and then decreasing like $\Omega^{-6}$. The maximal cross section is found for the photon wavevector $k \sim k_{F}$, the Fermi surface size, which typically means a photon energy $\hbar \Omega$ in the keV range. Possible experiments aimed at checking the existence of these rare but seemingly measurable elastic photon–photon scattering processes are discussed, using in particular intense synchrotron sources. |
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