514 research outputs found
Anatomy of a Bounce
Holographic considerations are used in the scrutiny of a special class of
brane-world cosmologies. Inherently to this class, the brane typically bounces,
at a finite size, as a consequence of a charged black hole in the bulk. Whereas
a prior treatment [hep-th/0301010] emphasized a brane that is void of
standard-model matter, the analysis is now extended to include an intrinsic
(radiation-dominated) matter source. An interesting feature of this generalized
model is that a bounce is no longer guaranteed but, rather, depends on the
initial conditions. Ultimately, we demonstrate that compliance with an
appropriate holographic bound is a sufficient prerequisite for a bounce to
occur.Comment: 14 pages, Revtex; (v2) minor revisions; (v3) reference adde
Entropy Corrections for Schwarzschild and Reissner-Nordstr\"om Black Holes
Schwarzschild black hole being thermodynamically unstable, corrections to its
entropy due to small thermal fluctuations cannot be computed. However, a
thermodynamically stable Schwarzschild solution can be obtained within a cavity
of any finite radius by immersing it in an isothermal bath. For these boundary
conditions, classically there are either two black hole solutions or no
solution. In the former case, the larger mass solution has a positive specific
heat and hence is locally thermodynamically stable. We find that the entropy of
this black hole, including first order fluctuation corrections is given by:
{\cal S} = S_{BH} - \ln[\f{3}{R} (S_{BH}/4\p)^{1/2} -2]^{-1} + (1/2)
\ln(4\p), where is its Bekenstein-Hawking entropy and is the
radius of the cavity. We extend our results to four dimensional
Reissner-Nordstr\"om black holes, for which the corresponding expression is:
{\cal S} = S_{BH} - \f{1}{2} \ln [ {(S_{BH}/\p R^2) ({3S_{BH}}/{\p R^2} -
2\sqrt{{S_{BH}}/{\p R^2 -\a^2}}) \le(\sqrt{{S_{BH}}/{\p R^2}} - \a^2 \ri)}/
{\le({S_{BH}}/{\p R^2} -\a^2 \ri)^2} ]^{-1} +(1/2)\ln(4\p). Finally, we
generalise the stability analysis to Reissner-Nordstr\"om black holes in
arbitrary spacetime dimensions, and compute their leading order entropy
corrections. In contrast to previously studied examples, we find that the
entropy corrections in these cases have a different character.Comment: 6 pages, Revtex. References added, minor changes. Version to appear
in Class. Quant. Gra
Delocalization of brane gravity by a bulk black hole
We investigate the analogue of the Randall-Sundrum brane-world in the case
when the bulk contains a black hole. Instead of the static vacuum Minkowski
brane of the RS model, we have an Einstein static vacuum brane. We find that
the presence of the bulk black hole has a dramatic effect on the gravity that
is felt by brane observers. In the RS model, the 5D graviton has a stable
localized zero-mode that reproduces 4D gravity on the brane at low energies.
With a bulk black hole, there is no such solution -- gravity is delocalized by
the 5D horizon. However, the brane does support a discrete spectrum of
metastable massive bound states, or quasinormal modes, as was recently shown to
be the case in the RS scenario. These states should dominate the high frequency
component of the bulk gravity wave spectrum on a cosmological brane. We expect
our results to generalize to any bulk spacetime containing a Killing horizon.Comment: 7 pages, 6 figure
Quantum Gravity and Recovery of Information in Black Hole Evaporation
The Generalized Uncertainty Principle (GUP), motivated by current
alternatives of quantum gravity, produces significant modifications to the
Hawking radiation and the final stage of black hole evaporation. We show that
incorporation of the GUP into the quantum tunneling process (based on the
null-geodesic method) causes correlations between the tunneling probability of
different modes in the black hole radiation spectrum. In this manner, the
quantum information becomes encrypted in the Hawking radiation, and information
can be recovered as non-thermal GUP correlations between tunneling
probabilities of different modes.Comment: 7 pages, no figure, final revisio
Quasi-normal Modes of Electromagnetic Perturbations of Four-Dimensional Topological Black Holes with Scalar Hair
We study the perturbative behaviour of topological black holes with scalar
hair. We calculate both analytically and numerically the quasi-normal modes of
the electromagnetic perturbations. In the case of small black holes we find
evidence of a second-order phase transition of a topological black hole to a
hairy configuration.Comment: v2: 19 pages, 2 figures, added references, improved discussion, to
appear in JHE
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