65 research outputs found
Are There Topological Black Hole Solitons in String Theory?
We point out that the celebrated Hawking effect of quantum instability of
black holes seems to be related to a nonperturbative effect in string theory.
Studying quantum dynamics of strings in the gravitational background of black
holes we find classical instability due to emission of massless string
excitations. The topology of a black hole seems to play a fundamental role in
developing the string theory classical instability due to the effect of sigma
model instantons. We argue that string theory allows for a qualitative
description of black holes with very small masses and it predicts topological
solitons with quantized spectrum of masses. These solitons would not decay into
string massless excitations but could be pair created and may annihilate also.
Semiclassical mass quantization of topological solitons in string theory is
based on the argument showing existence of nontrivial zeros of beta function of
the renormalization group.Comment: 12 pages, TeX, requires phyzzx.tex, published in Gen. Rel. Grav. 19
(1987) 1173; comment added on December 18, 199
Geometrothermodynamics of the Kehagias-Sfetsos Black Hole
The application of information geometric ideas to statistical mechanics using
a metric on the space of states, pioneered by Ruppeiner and Weinhold, has
proved to be a useful alternative approach to characterizing phase transitions.
Some puzzling anomalies become apparent, however, when these methods are
applied to the study of black hole thermodynamics. A possible resolution was
suggested by Quevedo et al. who emphasized the importance of Legendre
invariance in thermodynamic metrics. They found physically consistent results
for various black holes when using a Legendre invariant metric, which agreed
with a direct determination of the properties of phase transitions from the
specific heat.
Recently, information geometric methods have been employed by Wei et al. to
study the Kehagias-Sfetsos (KS) black hole in Horava-Lifshitz gravity. The
formalism suggests that a coupling parameter in this theory plays a role
analogous to the charge in Reissner-Nordstrom (RN) black holes or angular
momentum in the Kerr black hole and calculation of the specific heat shows a
singularity which may be interpreted as a phase transition. When the curvature
of the Ruppeiner metric is calculated for such a theory it does not, however,
show a singularity at the phase transition point.
We show that the curvature of a particular Legendre invariant ("Quevedo")
metric for the KS black hole is singular at the phase transition point. We
contrast the results for the Ruppeiner, Weinhold and Quevedo metrics and in the
latter case investigate the consistency of taking either the entropy or mass as
the thermodynamic potential.Comment: v2: some references adde
Entropy of Rotating Misner String Spacetimes
Using a boundary counterterm prescription motivated by the AdS/CFT
conjecture, I evaluate the energy, entropy and angular momentum of the class of
Kerr-NUT/bolt-AdS spacetimes. As in the non-rotating case, when the NUT charge
is nonzero the entropy is no longer equal to one-quarter of the area due to the
presence of the Misner string. When the cosmological constant is also non-zero,
the entropy is bounded from above.Comment: Revtex, 9 pages, 3 figure
Misner String Entropy
I show that gravitational entropy can be ascribed to spacetimes containing
Misner strings (the gravitational analogues of Dirac strings), even in the
absence of any other event horizon (or bolt) structures. This result follows
from an extension of proposals for evaluating the stress-energy of a
gravitational system which are motivated by the AdS/CFT correspondence.Comment: revtex, 5 pages, references added, typo correcte
Charge conservation and time-varying speed of light
It has been recently claimed that cosmologies with time dependent speed of
light might solve some of the problems of the standard cosmological scenario,
as well as inflationary scenarios. In this letter we show that most of these
models, when analyzed in a consistent way, lead to large violations of charge
conservation. Thus, they are severly constrained by experiment, including those
where is a power of the scale factor and those whose source term is the
trace of the energy-momentum tensor. In addition, early Universe scenarios with
a sudden change of related to baryogenesis are discarded.Comment: 4 page
Quasilocal Thermodynamics of Kerr de Sitter Spacetimes and the dS/CFT Correspondence
We consider the quasilocal thermodynamics of rotating black holes in
asymptotic de Sitter spacetimes. Using the minimal number of intrinsic boundary
counterterms, we carry out an analysis of the quasilocal thermodynamics of
Kerr-de Sitter black holes for virtually all possible values of the mass,
rotation parameter and cosmological constant that leave the quasilocal boundary
inside the cosmological event horizon. Specifically, we compute the quasilocal
energy, the conserved charges, the temperature and the heat capacity for the
-dimensional Kerr-dS black holes. We perform a quasilocal stability
analysis and find phase behavior that is commensurate with previous analysis
carried out through the use of Arnowitt-Deser-Misner (ADM) parameters. Finally,
we investigate the non-rotating case analytically.Comment: RevTeX4, 19 pages, 11 figures, a few typos fixed, the version to be
published in Phys. Rev. D6
Quasilocal Thermodynamics of Kerr and Kerr-anti-de Sitter Spacetimes and the AdS/CFT Correspondence
We consider the quasilocal thermodynamics of rotating black holes in
asymptotically flat and asymptotically anti de Sitter spacetimes. Using the
minimal number of intrinsic boundary counterterms inspired by the AdS/CFT
correspondence, we find that we are able to carry out an analysis of the
thermodynamics of these black holes for virtually all possible values of the
rotation parameter and cosmological constant that leave the quasilocal boundary
well-defined, going well beyond what is possible with background subtraction
methods. Specifically, we compute the quasilocal energy and angular
momentum for arbitrary values of the rotation, mass and cosmological
constant parameters for the 3+1 dimensional Kerr, Kerr-AdS black holes and 2+1
dimensional BTZ black hole. We perform a quasilocal stability analysis and find
phase behavior that is commensurate with previous analyses carried out at
infinity.Comment: Latex, 43 pages, 22 eps figures, several typos corrected, final
version to appear in Phys. Rev.
Charged rotating dilaton black branes in AdS universe
We present the metric for the -dimensional charged rotating dilaton
black branes with cylindrical or toroidal horizons in the background of anti-de
Sitter spacetime. We find the suitable counterterm which removes the
divergences of the action in the presence of the dilaton potential in all
higher dimensions. We plot the Penrose diagrams of the spacetime and reveal
that the spacetime geometry crucially modifies in the presence of the dilaton
field. The conserved and thermodynamic quantities of the black branes are also
computed.Comment: 13 pages, 3 figures, to appear in Gen. Relat. Gravi
Ricci flat rotating black branes with a conformally invariant Maxwell source
We consider Einstein gravity coupled to an gauge field for which the
density is given by a power of the Maxwell Lagrangian. In -dimensions the
action of Maxwell field is shown to enjoy the conformal invariance if the power
is chosen as . We present a class of charge rotating solutions in
Einstein-conformally invariant Maxwell gravity in the presence of a
cosmological constant. These solutions may be interpreted as black brane
solutions with inner and outer event horizons or an extreme black brane
depending on the value of the mass parameter. Since we are considering power of
the Maxwell density, the black brane solutions exist only for dimensions which
are multiples of four. We compute conserved and thermodynamics quantities of
the black brane solutions and show that the expression of the electric field
does not depend on the dimension. Also, we obtain a Smarr-type formula and show
that these conserved and thermodynamic quantities of black branes satisfy the
first law of thermodynamics. Finally, we study the phase behavior of the
rotating black branes and show that there is no Hawking--Page phase transition
in spite of conformally invariant Maxwell field.Comment: 13 pages, one figur
Higgs Scalar-Tensor Theory for Gravity and the Flat Rotation Curves of Spiral Galaxies
The scalar-tensor theory of gravity with the Higgs field as scalar field is
presented. For central symmetry it reproduces the empirically measured flat
rotation curves of galaxies. We approximate the galaxy by a polytropic gas
sphere with the polytropic index and a massive core.Comment: 17 pages, 12 figure
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