224 research outputs found
Exact solutions of Dirac equation on (1+1)-dimensional spacetime coupled to a static scalar field
We use a generalized scheme of supersymmetric quantum mechanics to obtain the
energy spectrum and wave function for Dirac equation in (1+1)-dimensional
spacetime coupled to a static scalar field.Comment: 7 pages, Late
The black hole final state
We propose that in quantum gravity one needs to impose a final state boundary
condition at black hole singularities. This resolves the apparent contradiction
between string theory and semiclassical arguments over whether black hole
evaporation is unitary.Comment: 17 pages, harvmac, 1 figure, v2: comment about interactions and
references adde
Phase Transition of Electrically Charged Ricci-flat Black Holes
We study phase transition between electrically charged Ricci-flat black holes
and AdS soliton spacetime of Horowitz and Myers in five dimensions. Boundary
topology for both of them is . We consider
Reissner-Nordstrom black hole and R-charged black holes and find that phase
transition of these black holes to AdS soliton spacetime depends on the
relative size of two boundary circles. We also perform the stability analysis
for these black holes. In order to use the AdS/CFT correspondence, we work in
the grand canonical ensemble.Comment: 33 pages, 9 figures, Version 2, References adde
Nuttier Bubbles
We construct new explicit solutions of general relativity from double
analytic continuations of Taub-NUT spacetimes. This generalizes previous
studies of 4-dimensional nutty bubbles. One 5-dimensional locally
asymptotically AdS solution in particular has a special conformal boundary
structure of . We compute its boundary stress tensor and
relate it to the properties of the dual field theory. Interestingly enough, we
also find consistent 6-dimensional bubble solutions that have only one timelike
direction. The existence of such spacetimes with non-trivial topology is
closely related to the existence of the Taub-NUT(-AdS) solutions with more than
one NUT charge. Finally, we begin an investigation of generating new solutions
from Taub-NUT spacetimes and nuttier bubbles. Using the so-called Hopf duality,
we provide new explicit time-dependent backgrounds in six dimensions.Comment: 32 pages, 1 figure; v.3. typos corrected. Matches the published
versio
Instability of generalised AdS black holes and thermal field theory
We study black holes in AdS-like spacetimes, with the horizon given by an
arbitrary positive curvature Einstein metric. A criterion for classical
instability of such black holes is found in the large and small black hole
limits. Examples of large unstable black holes have a B\"ohm metric as the
horizon. These, classically unstable, large black holes are locally
thermodynamically stable. The gravitational instability has a dual description,
for example by using the version of the AdS/CFT
correspondence. The instability corresponds to a critical temperature of the
dual thermal field theory defined on a curved background.Comment: 1+16 pages. 1 figure. LaTeX. Minor clarification
Arrow of time in a recollapsing quantum universe
We show that the Wheeler-DeWitt equation with a consistent boundary condition
is only compatible with an arrow of time that formally reverses in a
recollapsing universe. Consistency of these opposite arrows is facilitated by
quantum effects in the region of the classical turning point. Since
gravitational time dilation diverges at horizons, collapsing matter must then
start re-expanding ``anticausally" (controlled by the reversed arrow) before
horizons or singularities can form. We also discuss the meaning of the
time-asymmetric expression used in the definition of ``consistent histories".
We finally emphasize that there is no mass inflation nor any information loss
paradox in this scenario.Comment: Many conceptual clarifications include
Classical and Thermodynamic Stability of Black Branes
It is argued that many non-extremal black branes exhibit a classical
Gregory-Laflamme instability if, and only if, they are locally
thermodynamically unstable. For some black branes, the Gregory-Laflamme
instability must therefore disappear near extremality. For the black -branes
of the type II supergravity theories, the Gregory-Laflamme instability
disappears near extremality for but persists all the way down to
extremality for (the black D3-brane is not covered by the analysis of
this paper). This implies that the instability also vanishes for the
near-extremal black M2 and M5-brane solutions.Comment: 21 pages, LaTeX. v2: Various points clarified, typos corrected and
reference adde
Glassy Phase Transition and Stability in Black Holes
Black hole thermodynamics, confined to the semi-classical regime, cannot
address the thermodynamic stability of a black hole in flat space. Here we show
that inclusion of correction beyond the semi-classical approximation makes a
black hole thermodynamically stable. This stability is reached through a phase
transition. By using Ehrenfest's scheme we further prove that this is a glassy
phase transition with a Prigogine-Defay ratio close to 3. This value is well
placed within the desired bound (2 to 5) for a glassy phase transition. Thus
our analysis indicates a very close connection between the phase transition
phenomena of a black hole and glass forming systems. Finally, we discuss the
robustness of our results by considering different normalisations for the
correction term.Comment: v3, minor changes over v2, references added, LaTeX-2e, 18 pages, 3 ps
figures, to appear in Eour. Phys. Jour.
Logarithmic Corrections to Rotating Extremal Black Hole Entropy in Four and Five Dimensions
We compute logarithmic corrections to the entropy of rotating extremal black
holes using quantum entropy function i.e. Euclidean quantum gravity approach.
Our analysis includes five dimensional supersymmetric BMPV black holes in type
IIB string theory on T^5 and K3 x S^1 as well as in the five dimensional CHL
models, and also non-supersymmetric extremal Kerr black hole and slowly
rotating extremal Kerr-Newmann black holes in four dimensions. For BMPV black
holes our results are in perfect agreement with the microscopic results derived
from string theory. In particular we reproduce correctly the dependence of the
logarithmic corrections on the number of U(1) gauge fields in the theory, and
on the angular momentum carried by the black hole in different scaling limits.
We also explain the shortcomings of the Cardy limit in explaining the
logarithmic corrections in the limit in which the (super)gravity description of
these black holes becomes a valid approximation. For non-supersymmetric
extremal black holes, e.g. for the extremal Kerr black hole in four dimensions,
our result provides a stringent testing ground for any microscopic explanation
of the black hole entropy, e.g. Kerr/CFT correspondence.Comment: LaTeX file, 50 pages; v2: added extensive discussion on the relation
between boundary condition and choice of ensemble, modified analysis for
slowly rotating black holes, all results remain unchanged, typos corrected;
v3: minor additions and correction
Two-dimensional Quantum-Corrected Eternal Black Hole
The one-loop quantum corrections to geometry and thermodynamics of black hole
are studied for the two-dimensional RST model. We chose boundary conditions
corresponding to the eternal black hole being in the thermal equilibrium with
the Hawking radiation. The equations of motion are exactly integrated. The one
of the solutions obtained is the constant curvature space-time with dilaton
being a constant function. Such a solution is absent in the classical theory.
On the other hand, we derive the quantum-corrected metric (\ref{solution})
written in the Schwarzschild like form which is a deformation of the classical
black hole solution \cite{5d}. The space-time singularity occurs to be milder
than in classics and the solution admits two asymptotically flat black hole
space-times lying at "different sides" of the singularity. The thermodynamics
of the classical black hole and its quantum counterpart is formulated. The
thermodynamical quantities (energy, temperature, entropy) are calculated and
occur to be the same for both the classical and quantum-corrected black holes.
So, no quantum corrections to thermodynamics are observed. The possible
relevance of the results obtained to the four-dimensional case is discussed.Comment: Latex, 28 pges; minor corrections in text and abstract made and new
references adde
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