105 research outputs found

    Quantum Corrections to Black Hole Entropy in String Theory

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    The one-loop contribution to the entropy of a black hole from field modes near the horizon is computed in string theory. It is modular invariant and ultraviolet finite. There is an infrared divergence that signifies an instability near the event horizon of the black hole. It is due to the exponential growth of the density of states and the associated Hagedorn transition characteristic of string theory. It is argued that this divergence is indicative of a tree level contribution, and the Bekenstein-Hawking-Gibbons formula for the entropy should be understood in terms of string states stuck near the horizon.Comment: 15 pages, harvmac, replaced with version published in Phys. Letts.

    On Condensation of Closed-string Tachyons

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    An F-theory dual of a nonsupersymmetric orientifold is considered. It is argued that the condensation of both open and closed string tachyons in the orientifold corresponds to the annihilation of branes and anti-branes in the F-theory dual. The end-point of tachyon condensation is thus expected to be the vacuum of Type-IIB superstring. Some speculations are presented about the F-theory dual of the bosonic string and tachyon condensation thereof.Comment: 16 pages, 2 figures, harvmac(b

    Exact Counting of Black Hole Microstates

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    The exact entropy of two-charge supersymmetric black holes in N=4 string theories is computed to all orders using Wald's formula and the supersymmetric attractor equations with an effective action that includes the relevant higher curvature terms. Classically, these black holes have zero area but the attractor equations are still applicable at the quantum level. The quantum corrected macroscopic entropy agrees precisely with the microscopic counting for an infinite tower of fundamental string states to all orders in an asymptotic expansion.Comment: 4 pages, latex, minor change

    Black hole entropy and attractors

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    The introductory lectures delivered at the 2006 RTN Winter School on Strings, Supergravity and Gauge Theories at CERN and the 2005 Shanghai Summer School on Recent Trends in M/String Theory were aimed at Ph.D students and recent postdocs. We describe recent progress in understanding quantum aspects of black holes after reviewing the relevant background material, and illustrate the basic concepts with a few examples

    Discrete Flux as Quantum Hair

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    We investigate Yang-Mills theory on a spatial torus at finite temperature in the presence of discrete electric and magnetic fluxes using the AdS/CFT correspondence. We calculate the leading dependence of the partition function on the fluxes using the dual supergravity theory and comment upon the interpretation of these fluxes as discrete quantum hair for black holes in AdS spacetime.Comment: 15 pages, LaTex, no figure

    Strings on a cone and black hole entropy

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    String propagation on a cone with deficit angle 2π (1 - 1/N) is described by constructing a non-compact orbifold of a plane by a ZN subgroup of rotations. It is modular invariant and has tachyons in the twisted sectors that are localized at the tip of the cone. A possible connection with the quantum corrections to the black hole entropy is outlined. The entropy computed by analytically continuing in N would receive contribution only from the twisted sectors and be naturally proportional to the area of the event horizon. Evidence is presented for a new duality for these orbifolds similar to the R →1/R duality

    String Islands

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    We discuss string theories with small numbers of non-compact moduli and describe constructions of string theories whose low-energy limit is described by various pure supergravity theories. We also construct a D=4,N=4 compactification of type II string theory with 34 vector fields.Comment: An erroneous example removed. We thank Massimo Bianchi and Cumrun Vafa for pointing out this erro
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