130 research outputs found
Black Hole Entropy and Superconformal Field Theories on Brane-Antibrane Systems
We obtain the enropy of Schwarzschild and charged black holes in D>4 from
superconformal gases that live on p=10-D dimensional brane-antibrane systems
wrapped on T^p. The preperties of the strongly coupled superconformal theories
such as the appearance of hidden dimensions (for p=1,4) and fractional strings
(for p=5) are crucial for our results. In all cases, the Schwarzschild radius
is given by the transverse fluctuations of the branes and antibranes due to the
finite temperature. We show that our results can be generalized to multicharged
black holes.Comment: 24 pages in phyzzx.te
PP-wave Black holes and The Matrix Model
We discuss the sizes of a black hole in the M theory pp-wave background, and
how the transverse size can be reproduced in the matrix model.Comment: 12 pages, harvmac. v2: final version to be published in JHEP, refs.
adde
Extracting the bulk metric from boundary information in asymptotically AdS spacetimes
We use geodesic probes to recover the entire bulk metric in certain
asymptotically AdS spacetimes. Given a spectrum of null geodesic endpoints on
the boundary, we describe two remarkably simple methods for recovering the bulk
information. After examining the issues which affect their application in
practice, we highlight a significant advantage one has over the other from a
computational point of view, and give some illustrative examples. We go on to
consider spacetimes where the methods cannot be used to recover the complete
bulk metric, and demonstrate how much information can be recovered in these
cases.Comment: 33 pages, 11 figures; v2 references adde
The Entropy of the Rotating Charged Black Threebrane from a Brane-Antibrane System
We show that a model based on a D3-brane--anti-D3-brane system at finite
temperature, proposed previously as a microscopic description of the
non-rotating black threebrane of type IIB supergravity arbitrarily far from
extremality, can also successfully reproduce the entropy of the rotating
threebrane with arbitrary charge (including the neutral case, which corresponds
to the Kerr black hole in seven dimensions). Our results appear to confirm in
particular the need for a peculiar condition on the energy of the two gases
involved in the model, whose physical interpretation remains to be elucidated.Comment: 12 pages, references added in section 1 and
On Witten's Instability and Winding Tachyons
We investigate, from a spacetime perspective, some aspects of Horowitz's
recent conjecture that black strings may catalyze the decay of Kaluza-Klein
spacetimes into a bubble of nothing. We identify classical configurations that
interpolate between flat space and the bubble, and discuss the energetics of
the transition. We investigate the effects of winding tachyons on the size and
shape of the barrier and find no evidence at large compactification radius that
tachyons enhance the tunneling rate. For the interesting radii, of order the
string scale, the question is difficult to answer due to the failure of the
expansion.Comment: 15 pages, 2 figures, Late
Excursions beyond the horizon: Black hole singularities in Yang-Mills theories (I)
We study black hole singularities in the AdS/CFT correspondence. These
singularities show up in CFT in the behavior of finite-temperature correlation
functions. We first establish a direct relation between space-like geodesics in
the bulk and momentum space Wightman functions of CFT operators of large
dimensions. This allows us to probe the regions inside the horizon and near the
singularity using the CFT. Information about the black hole singularity is
encoded in the exponential falloff of finite-temperature correlators at large
imaginary frequency. We construct new gauge invariant observables whose
divergences reflect the presence of the singularity. We also find a UV/UV
connection that governs physics inside the horizon. Additionally, we comment on
the possible resolution of the singularity.Comment: 34 page, 10 figures, uses harvmac, references adde
A Space-Time Orbifold: A Toy Model for a Cosmological Singularity
We explore bosonic strings and Type II superstrings in the simplest time
dependent backgrounds, namely orbifolds of Minkowski space by time reversal and
some spatial reflections. We show that there are no negative norm physical
excitations. However, the contributions of negative norm virtual states to
quantum loops do not cancel, showing that a ghost-free gauge cannot be chosen.
The spectrum includes a twisted sector, with strings confined to a ``conical''
singularity which is localized in time. Since these localized strings are not
visible to asymptotic observers, interesting issues arise regarding unitarity
of the S-matrix for scattering of propagating states. The partition function of
our model is modular invariant, and for the superstring, the zero momentum
dilaton tadpole vanishes. Many of the issues we study will be generic to
time-dependent cosmological backgrounds with singularities localized in time,
and we derive some general lessons about quantizing strings on such spaces.Comment: 21 pages, 2 figure
Holographic Description of AdS Cosmologies
To gain insight in the quantum nature of the big bang, we study the dual
field theory description of asymptotically anti-de Sitter solutions of
supergravity that have cosmological singularities. The dual theories do not
appear to have a stable ground state. One regularization of the theory causes
the cosmological singularities in the bulk to turn into giant black holes with
scalar hair. We interpret these hairy black holes in the dual field theory and
use them to compute a finite temperature effective potential. In our study of
the field theory evolution, we find no evidence for a "bounce" from a big
crunch to a big bang. Instead, it appears that the big bang is a rare
fluctuation from a generic equilibrium quantum gravity state.Comment: 34 pages, 8 figures, v2: minor changes, references adde
Anti-Periodic Boundary Conditions in Supersymmetric DLCQ
It is of considerable importance to have a numerical method for solving
supersymmetric theories that can support a non-zero central charge. The central
charge in supersymmetric theories is in general a boundary integral and
therefore vanishes when one uses periodic boundary conditions. One is therefore
prevented from studying BPS states in the standard supersymmetric formulation
of DLCQ (SDLCQ). We present a novel formulation of SDLCQ where the fields
satisfy anti-periodic boundary conditions. The Hamiltonian is written as the
anti-commutator of two charges, as in SDLCQ. The anti-periodic SDLCQ we
consider breaks supersymmetry at finite resolution, but requires no
renormalization and becomes supersymmetric in the continuum limit. In
principle, this method could be used to study BPS states. However, we find its
convergence to be disappointingly slow.Comment: 9pp, 2 figure
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