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1,127
A new cosmological scenario in string theory,” Phys
 Rev. D
, 2002
"... We consider new cosmological solutions with a collapsing, an intermediate and an expanding phase. The boundary between the expanding (collapsing) phase and the intermediate phase is seen by comoving observers as a cosmological past (future) horizon. The solutions are naturally embedded in string and ..."
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Cited by 91 (5 self)
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We consider new cosmological solutions with a collapsing, an intermediate and an expanding phase. The boundary between the expanding (collapsing) phase and the intermediate phase is seen by comoving observers as a cosmological past (future) horizon. The solutions are naturally embedded in string and M–theory. In the particular case of a two–dimensional cosmology, space–time is flat with an identification under boost and translation transformations. We consider the corresponding string theory orbifold and calculate the modular invariant one–loop partition function. In this case there is a strong parallel with the BTZ black hole. The higher dimensional cosmologies have a time–like curvature singularity in the intermediate region. In some cases the string coupling can be made small throughout all of space–time but string corrections become important at the singularity. This happens where string winding modes become light which could resolve the singularity. The new proposed space–time causal structure could have implications for cosmology, independently of string theory.
The Thermodynamics of Black Holes
, 2000
"... We review the present status of black hole thermodynamics. Our review includes discussion of classical black hole thermodynamics, Hawking radiation from black holes, the generalized second law, and the issue of entropy bounds. A brief survey also is given of approaches to the calculation of black ho ..."
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Cited by 68 (0 self)
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We review the present status of black hole thermodynamics. Our review includes discussion of classical black hole thermodynamics, Hawking radiation from black holes, the generalized second law, and the issue of entropy bounds. A brief survey also is given of approaches to the calculation of black hole entropy. We conclude with a discussion of some unresolved open issues.
The generally covariant locality principle  A new paradigm for local quantum physics
 COMMUN.MATH.PHYS
, 2001
"... A new approach to the modelindependent description of quantum field theories will be introduced in the present work. The main feature of this new approach is to incorporate in a local sense the principle of general covariance of general relativity, thus giving rise to the concept of a locally cova ..."
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Cited by 66 (13 self)
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A new approach to the modelindependent description of quantum field theories will be introduced in the present work. The main feature of this new approach is to incorporate in a local sense the principle of general covariance of general relativity, thus giving rise to the concept of a locally covariant quantum field theory. Such locally covariant quantum field theories will be described mathematically in terms of covariant functors between the categories, on one side, of globally hyperbolic spacetimes with isometric embeddings as morphisms and, on the other side, of ∗algebras with unital injective ∗endomorphisms as morphisms. Moreover, locally covariant quantum fields can be described in this framework as natural transformations between certain functors. The usual HaagKastler framework of nets of operatoralgebras over a fixed spacetime backgroundmanifold, together with covariant automorphic actions of the isometrygroup of the background spacetime, can be regained from this new approach as a special case. Examples of this new approach are also outlined. In case that a locally covariant quantum field theory obeys the
NonTuring computations via MalamentHogarth spacetimes
 Int. J. Theoretical Phys
, 2002
"... We investigate the Church–Kalmár–Kreisel–Turing Theses concerning theoretical (necessary) limitations of future computers and of deductive sciences, in view of recent results of classical general relativity theory. We argue that (i) there are several distinguished Church–Turingtype Theses (not only ..."
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Cited by 66 (8 self)
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We investigate the Church–Kalmár–Kreisel–Turing Theses concerning theoretical (necessary) limitations of future computers and of deductive sciences, in view of recent results of classical general relativity theory. We argue that (i) there are several distinguished Church–Turingtype Theses (not only one) and (ii) validity of some of these theses depend on the background physical theory we choose to use. In particular, if we choose classical general relativity theory as our background theory, then the above mentioned limitations (predicted by these Theses) become no more necessary, hence certain forms of the Church– Turing Thesis cease to be valid (in general relativity). (For other choices of the background theory the answer might be different.) We also look at various “obstacles ” to computing a nonrecursive function (by relying on relativistic phenomena) published in the literature and show that they can be avoided (by improving the “design ” of our future computer). We also ask ourselves, how all this reflects on the arithmetical hierarchy and the analytical hierarchy of uncomputable functions.
Higher dimensional black holes and supersymmetry,” Phys. Rev. D 68 (2003) 024024 [Erratumibid
 Rev. D68 (2003) 105009 [Erratumibid. D70 (2004) 089901] [hepth/0304064
"... hepth/0211290 It has recently been shown that the uniqueness theorem for stationary black holes cannot be extended to five dimensions. However, uniqueness is an important assumption of the string theory black hole entropy calculations. This paper justifies this assumption by proving a uniqueness th ..."
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Cited by 65 (11 self)
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hepth/0211290 It has recently been shown that the uniqueness theorem for stationary black holes cannot be extended to five dimensions. However, uniqueness is an important assumption of the string theory black hole entropy calculations. This paper justifies this assumption by proving a uniqueness theorem for supersymmetric black holes in five dimensions. Some remarks concerning general properties of nonsupersymmetric higher dimensional black holes are made. It is conjectured that there exist new families of stationary higher dimensional black hole solutions with fewer symmetries than any known solution. 1
Deviations from the Area Law for Supersymmetric Black Holes
, 1999
"... We review modifications of the BekensteinHawking area law for black hole entropy in the presence of higherderivative interactions. In fourdimensional N = 2 compactifications of string theory or Mtheory these modifications are crucial for finding agreement between the macroscopic entropy obtained ..."
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Cited by 61 (3 self)
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We review modifications of the BekensteinHawking area law for black hole entropy in the presence of higherderivative interactions. In fourdimensional N = 2 compactifications of string theory or Mtheory these modifications are crucial for finding agreement between the macroscopic entropy obtained from supergravity and the microscopic entropy obtained by counting states in string or Mtheory. Our discussion is based on the effective Wilsonian action, which in the context of N = 2 supersymmetric theories is defined in terms of holomorphic quantities. At the end we briefly indicate how to incorporate nonholomorphic corrections. March 1999 a cardoso@phys.uu.nl b bdewit@phys.uu.nl c mohaupt@hera1.physik.unihalle.de 1 Introduction It is one of the most intriguing properties of black holes in general relativity that one can derive a set of laws, called the laws of black hole mechanics, which are formally equivalent to the laws of thermodynamics [1]. For instance, the first law of ...
The prebig bang scenario in string cosmology
 Phys. Rept
, 2003
"... We review physical motivations, phenomenological consequences, and open problems of the socalled prebig bang scenario in superstring cosmology. Contents 1 ..."
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Cited by 56 (2 self)
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We review physical motivations, phenomenological consequences, and open problems of the socalled prebig bang scenario in superstring cosmology. Contents 1
A closed, expanding universe in string theory,” Phys
 Lett. B
, 1992
"... We present a conformal field theory – obtained from a gauged WZW model – that describes a closed, inhomogeneous expanding and recollapsing universe in 3 + 1 dimensions. A possible violation of cosmic censorship is avoided because the universe recollapses just when a naked singularity was about to fo ..."
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Cited by 51 (0 self)
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We present a conformal field theory – obtained from a gauged WZW model – that describes a closed, inhomogeneous expanding and recollapsing universe in 3 + 1 dimensions. A possible violation of cosmic censorship is avoided because the universe recollapses just when a naked singularity was about to form. The model has been chosen to have c = 4 (or ĉ = 4 in the supersymmetric case), just like four dimensional Minkowski space.
Reall, “Nearhorizon symmetries of extremal black holes
"... Recent work has demonstrated an attractor mechanism for extremal rotating black holes subject to the assumption of a nearhorizon SO(2, 1) symmetry. We prove the existence of this symmetry for any extremal black hole with the same number of rotational symmetries as known four and five dimensional so ..."
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Cited by 50 (3 self)
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Recent work has demonstrated an attractor mechanism for extremal rotating black holes subject to the assumption of a nearhorizon SO(2, 1) symmetry. We prove the existence of this symmetry for any extremal black hole with the same number of rotational symmetries as known four and five dimensional solutions (including black rings). The result is valid for a general twoderivative theory of gravity coupled to abelian vectors and uncharged scalars, allowing for a nontrivial scalar potential. We prove that it remains valid in the presence of higherderivative corrections. We show that SO(2, 1)symmetric nearhorizon solutions can be analytically continued to give SU(2)symmetric black hole solutions. For example, the nearhorizon limit of an extremal 5D MyersPerry black hole is related by analytic continuation to a nonextremal cohomogeneity1 MyersPerry solution. 1
Acoustic black holes: Horizons, ergospheres, and Hawking
, 1998
"... grqc/9712010 It is a deceptively simple question to ask how acoustic disturbances propagate in a nonhomogeneous flowing fluid. Subject to suitable restrictions, this question can be answered by invoking the language of Lorentzian differential geometry. I begin this paper with a pedagogical derivat ..."
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Cited by 48 (24 self)
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grqc/9712010 It is a deceptively simple question to ask how acoustic disturbances propagate in a nonhomogeneous flowing fluid. Subject to suitable restrictions, this question can be answered by invoking the language of Lorentzian differential geometry. I begin this paper with a pedagogical derivation of the following result: If the fluid is barotropic and inviscid, and the flow is irrotational (though possibly time dependent), then the equation of motion for the velocity potential describing a sound wave is identical to that for a minimally coupled massless scalar field propagating in a (3 + 1)–dimensional Lorentzian geometry ∆ψ ≡ 1 ( √) µν