105 research outputs found
Quantum Corrections to Black Hole Entropy in String Theory
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
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
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
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
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
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
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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