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31
Phases of quantum gravity in AdS(3) and linear dilaton backgrounds
 2005) [arXiv:hepth/0503121]. – 37 – K. Gawedzki, “Noncompact WZW conformal field theories,” arXiv:hepth/9110076
"... We show that string theory in AdS3 has two distinct phases depending on the radius of curvature RAdS = √ kls. For k> 1 (i.e. RAdS> ls), the SL(2,C) invariant vacuum of the spacetime conformal field theory is normalizable, the high energy density of states is given by the Cardy formula with ce ..."
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Cited by 20 (9 self)
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We show that string theory in AdS3 has two distinct phases depending on the radius of curvature RAdS = √ kls. For k> 1 (i.e. RAdS> ls), the SL(2,C) invariant vacuum of the spacetime conformal field theory is normalizable, the high energy density of states is given by the Cardy formula with ceff = c, and generic high energy states look like large BTZ black holes. For k < 1, the SL(2,C) invariant vacuum as well as BTZ black holes are nonnormalizable, ceff < c, and high energy states correspond to long strings that extend to the boundary of AdS3 and become more and more weakly coupled there. A similar picture is found in asymptotically linear dilaton spacetime with dilaton gradient Q = k.). The states responsible The entropy grows linearly with the energy in this case (for k> 1 2 for this growth are two dimensional black holes for k> 1, and highly excited perturbative strings living in the linear dilaton throat for k < 1. The change of behavior at k = 1 in the two cases is an example of a string/black hole transition. The entropies of black holes and strings coincide at k = 1. 2
Heterotic strings in two dimensions and new stringy phase transitions
 JHEP
"... We discuss heterotic string theories in two dimensions with gauge groups Spin(24) and Spin(8) × E8. After compactification the theories exhibit a rich spectrum of states with both winding and momentum. At special points some of these stringy states become massless, leading to new first order phase ..."
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Cited by 18 (2 self)
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We discuss heterotic string theories in two dimensions with gauge groups Spin(24) and Spin(8) × E8. After compactification the theories exhibit a rich spectrum of states with both winding and momentum. At special points some of these stringy states become massless, leading to new first order phase transitions. For example, the thermal theories exhibit standard thermodynamics below the phase transition, but novel and peculiar behavior above it. In particular, when the radius of the Euclidean circle is smaller than the phase transition point the torus partition function is not given by the thermal trace over the spacetime Hilbert space. The full moduli space of compactified theories is 13 dimensional, when Wilson lines are included; the Spin(24) and Spin(8)×E8 theories correspond to distinct decompactification limits
On Black Hole Thermodynamics of 2D Type 0A
, 2005
"... Abstract:We present a detailed analysis of the thermodynamics of two dimensional black hole solutions to type 0A with q units of electric and magnetic °ux. We compute the free energy and derived quantities such as entropy and mass for an arbitrary nonextremal black hole. The free energy is nonvani ..."
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Cited by 16 (2 self)
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Abstract:We present a detailed analysis of the thermodynamics of two dimensional black hole solutions to type 0A with q units of electric and magnetic °ux. We compute the free energy and derived quantities such as entropy and mass for an arbitrary nonextremal black hole. The free energy is nonvanishing, in contrast to the case of dilatonic 2d black holes without electric and magnetic °uxes. The entropy of the extremal black holes is obtained, and we ¯nd it to be proportional to q2, the square of the RR °ux. We compare these thermodynamics quantities with those from candidate matrix model duals.
Fundamental strings and black holes
 JHEP
, 2007
"... We propose a black hole thermodynamic description of highly excited charged and uncharged perturbative string states in 3 + 1 dimensional type II and 4 + 1 dimensional heterotic string theory. We also discuss the generalization to extremal and nonextremal black holes carrying magnetic charges. 11/0 ..."
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Cited by 15 (1 self)
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We propose a black hole thermodynamic description of highly excited charged and uncharged perturbative string states in 3 + 1 dimensional type II and 4 + 1 dimensional heterotic string theory. We also discuss the generalization to extremal and nonextremal black holes carrying magnetic charges. 11/06
Boundary counterterms and the thermodynamics of 2D black holes,” arXiv:hepth/0411121
"... We utilize a novel method to study the thermodynamics of two dimensional type 0A black holes with constant RR flux. Our approach is based on the HamiltonJacobi method of deriving boundary counterterms. We demonstrate this approach by recovering the standard results for a well understood example, Wi ..."
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Cited by 15 (3 self)
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We utilize a novel method to study the thermodynamics of two dimensional type 0A black holes with constant RR flux. Our approach is based on the HamiltonJacobi method of deriving boundary counterterms. We demonstrate this approach by recovering the standard results for a well understood example, Witten’s black hole. Between this example and the 0A black hole we find universal expressions for the entropy and black hole mass, as well as the infrared divergence of the partition function. As a nontrivial check of our results we verify the first law of thermodynamics for these systems. Our results for the mass disagree with the predictions of a proposed matrix model dual of the 0A black hole.
Beyond the singularity of the 2D charged black hole
 JHEP
, 2003
"... Abstract: Two dimensional charged black holes in string theory can be obtained as exact SL(2,IR)×U(1) quotient CFTs. The geometry of the quotient is induced from that of the U(1) group, and in particular includes regions beyond the black hole singularities. Moreover, wavefunctions in such black hole ..."
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Cited by 10 (8 self)
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Abstract: Two dimensional charged black holes in string theory can be obtained as exact SL(2,IR)×U(1) quotient CFTs. The geometry of the quotient is induced from that of the U(1) group, and in particular includes regions beyond the black hole singularities. Moreover, wavefunctions in such black holes are obtained from gauge invariant vertex operators in the SL(2, IR) CFT, hence their behavior beyond the singularity is determined. When the black hole is charged we find that the wavefunctions are smooth at the singularities, and the scattering waves prepared beyond the singularity are not fully reflected: Part of the wave is transmitted through the singularity. Such wavefunctions are fully reflected from the singularity of an uncharged black hole. But the physics outside the horizon of a charged black hole is sensitive to conditions set behind the past singularity. 1
Long Strings, Anomaly Cancellation, Phase Transitions, Tduality and Locality
 in the 2d Heterotic String,” [arXiv:hepth/0511220
"... We study the noncritical twodimensional heterotic string. Long fundamental strings play a crucial role in the dynamics. They cancel anomalies and lead to phase transitions when the system is compactified on a Euclidean circle. A careful analysis of the gauge symmetries of the system uncovers new su ..."
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Cited by 7 (1 self)
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We study the noncritical twodimensional heterotic string. Long fundamental strings play a crucial role in the dynamics. They cancel anomalies and lead to phase transitions when the system is compactified on a Euclidean circle. A careful analysis of the gauge symmetries of the system uncovers new subtleties leading to modifications of the worldsheet results. The compactification on a Euclidean thermal circle is particularly interesting. It leads us to an incompatibility between Tduality (and its corresponding gauge symmetry) and locality. 11/05
Noncritical heterotic superstrings in various dimensions
 JHEP
, 2006
"... We construct heterotic string theories on spacetimes of the form R d−1,1 ×N = 2 linear dilaton, where d = 6, 4, 2, 0. There are two lines of supersymmetric theories descending from the two supersymmetric tendimensional heterotic theories. These have gauge groups which are lower rank subgroups of E8 ..."
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Cited by 5 (1 self)
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We construct heterotic string theories on spacetimes of the form R d−1,1 ×N = 2 linear dilaton, where d = 6, 4, 2, 0. There are two lines of supersymmetric theories descending from the two supersymmetric tendimensional heterotic theories. These have gauge groups which are lower rank subgroups of E8×E8 and SO(32). On turning on a (2, 2) deformation which makes the two dimensional part a smooth SL2(IR)/U(1) supercoset, the gauge groups get broken further. In the deformed theories, there are nontrivial moduli which are charged under the surviving gauge group in the case of d = 6. We construct the marginal operators on the worldsheet corresponding to these moduli.
Black Holes in Two Dimensions
, 1998
"... Models of black holes in (1 + 1)dimensions provide a theoretical laboratory for the study of semiclassical effects of realistic black holes in Einstein’s theory. Important examples of twodimensional models are given by string theory motivated dilaton gravity, by ordinary general relativity in the ..."
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Cited by 4 (2 self)
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Models of black holes in (1 + 1)dimensions provide a theoretical laboratory for the study of semiclassical effects of realistic black holes in Einstein’s theory. Important examples of twodimensional models are given by string theory motivated dilaton gravity, by ordinary general relativity in the case of spherical symmetry, and by Poincaré gauge gravity in two spacetime dimensions. In this paper, we present an introductory overview of the exact solutions of twodimensional classical Poincaré gauge gravity (PGG). A general method is described with the help of which the gravitational field equations are solved for an arbitrary Lagrangian. The specific choice of a torsionrelated coframe plays a central role in this approach. Complete integrability of the general PGG model is demonstrated in vacuum, and the structure of the black hole type solutions of the quadratic models with and without matter is analyzed in detail. Finally, the integrability of the general dilaton gravity model is established by recasting it into an effective PGG model. file tworev8.tex, 19980714 1