23 research outputs found
Asymptotic Quasinormal Modes of d-Dimensional Schwarzschild Black Hole with Gauss-Bonnet Correction
We obtain an analytic expression for the highly damped asymptotic quasinormal
mode frequencies of the -dimensional Schwarzschild black hole modified
by the Gauss-Bonnet term, which appears in string derived models of gravity.
The analytic expression is obtained under the string inspired assumption that
there exists a minimum length scale in the system and in the limit when the
coupling in front of the Gauss-Bonnet term in the action is small. Although
there are several similarities of this geometry with that of the Schwarzschild
black hole, the asymptotic quasinormal mode frequencies are quite different. In
particular, the real part of the asymptotic quasinormal frequencies for this
class of single horizon black holes in not proportional to log(3).Comment: 10 pages, latex file, changes in several equations, changes in the
abstract qualitative nature of conclusions unaffecte
Universal near-horizon conformal structure and black hole entropy
It is shown that a massless scalar probe reveals a universal near-horizon
conformal structure for a wide class of black holes, including the BTZ. The
central charge of the corresponding Virasoro algebra contains information about
the black hole. With a suitable quantization condition on the central charge,
the CFT associated with the black hole in our approach is consistent with the
recent observation of Witten, where the dual theory for the BTZ in the AdS/CFT
framework has been identified with the construction of Frenkel, Lepowsky and
Meurman. This CFT admits the Fischer-Griess monster group as its symmetry. The
logarithm of the dimension of a specific representation of the monster group
has been identified by Witten as the entropy of the BTZ black hole. Our
algebraic approach shows that a wide class of black holes share the same
near-horizon conformal structure as that for the BTZ. With a suitable
quantization condition, the CFT's for all these black holes in our formalism
can be identified with the FLM model, although not through the AdS/CFT
correspondence. The corresponding entropy for the BTZ provides a lower bound
for the entropy of this entire class of black holes.Comment: References updated, text rearrange
Scalar field dynamics in warped AdS_3 black hole background
We study the normal modes of a scalar field in the background of a warped
AdS_3 black hole which arises in topologically massive gravity. We discuss the
normal mode spectrum using the brick wall boundary condition. In addition, we
investigate the possibility of a more general boundary condition for the scalar
field.Comment: 7 pages, one figure, revtex4, refs. added and minor modifications in
tex
Black hole phase transitions via Bragg-Williams
We argue that a convenient way to analyze instabilities of black holes in AdS
space is via Bragg-Williams construction of a free energy function. Starting
with a pedagogical review of this construction in condensed matter systems and
also its implementation to Hawking-Page transition, we study instabilities
associated with hairy black holes and also with the -charged black holes.
For the hairy black holes, an analysis of thermal quench is presented.Comment: 23 pages, 8 figures, a discussion on thermal quench and a new figure
have been added, typos correcte
Normal mode analysis for scalar fields in BTZ black hole background
We analyze the possibility of inequivalent boundary conditions for a scalar
field propagating in the BTZ black hole space-time. We find that for certain
ranges of the black hole parameters, the Klein-Gordon operator admits a
one-parameter family of self-adjoint extensions. For this range, the BTZ
space-time is not quantum mechanically complete. We suggest a physically
motivated method for determining the spectra of the Klein-Gordon operator.Comment: 6 pages, no figure, late
Quasinormal modes for tensor and vector type perturbation of Gauss Bonnet black holes using third order WKB approach
We obtain the quasinormal modes for tensor perturbations of Gauss-Bonnet (GB)
black holes in dimensions and vector perturbations in
and 8 dimensions using third order WKB formalism. The tensor perturbation for
black holes in is not considered because of the fact that it is unstable
to tensor mode perturbations. In the case of uncharged GB black hole, for both
tensor and vector perturbations, the real part of the QN frequency increases as
the Gauss-Bonnet coupling () increases. The imaginary part first
decreases upto a certain value of and then increases with
for both tensor and vector perturbations. For larger values of , the
QN frequencies for vector perturbation differs slightly from the QN frequencies
for tensorial one. It has also been shown that as , the
quasinormal mode frequency for tensor and vector perturbation of the
Schwarzschild black hole can be obtained. We have also calculated the
quasinormal spectrum of the charged GB black hole for tensor perturbations.
Here we have found that the real oscillation frequency increases, while the
imaginary part of the frequency falls with the increase of the charge. We also
show that the quasinormal frequencies for scalar field perturbations and the
tensor gravitational perturbations do not match as was claimed in the
literature. The difference in the result increases if we increase the GB
coupling.Comment: 17 pages, 11 figures, change in title and abstract, new equations and
results added for QN frequencies for vector perturbations, new referencees
adde