568 research outputs found
Charged Rotating Black Hole Formation from Thin Shell Collapse in Three Dimensions
The thin shell collapse leading to the formation of charged rotating black
holes in three dimensions is analyzed in the light of a recently developed
Hamiltonian formalism for these systems. It is proposed to demand, as a way to
reconcile the properties of an infinitely extended solenoid in flat space with
a magnetic black hole in three dimensions, that the magnetic field should
vanish just outside the shell. The adoption of this boundary condition results
in an exterior solution with a magnetic field different from zero at a finite
distance from the shell. The interior solution is also found and assigns
another interpretation, in a different context, to the magnetic solution
previously obtained by Cl\'{e}ment and by Hirschmann and Welch.Comment: 15 pages, no figures. Discussion on junction conditions and
conclusions enlarged. Few references added. Final version for MPL
Topological regularization and self-duality in four-dimensional anti-de Sitter gravity
It is shown that the addition of a topological invariant (Gauss-Bonnet term)
to the anti-de Sitter (AdS) gravity action in four dimensions recovers the
standard regularization given by holographic renormalization procedure. This
crucial step makes possible the inclusion of an odd parity invariant
(Pontryagin term) whose coupling is fixed by demanding an asymptotic (anti)
self-dual condition on the Weyl tensor. This argument allows to find the dual
point of the theory where the holographic stress tensor is related to the
boundary Cotton tensor as , which
has been observed in recent literature in solitonic solutions and hydrodynamic
models.
A general procedure to generate the counterterm series for AdS gravity in any
even dimension from the corresponding Euler term is also briefly discussed.Comment: 13 pages, no figures; enlarged discussion on self-duality condition
for AAdS spacetimes, references added, final version for PR
Information transfer through intraspecific interactions in a lycosid spider
The transfer of information during agonistic and sexual interactions between adults of Lycosa tarentula fascilventrls is studied. Information theory and correspondence analysis are applied to the intra-individual transition matrices. Information is quantitatively similar
regardless of the context and the sex. Similarity arises mainly from the transition
between motionless and approaching-signalling patterns. There are no pattems strongly
predicting the immediate retreat of the sender and there is a marked predictability of
females immediately attacking in their agonistic interactions. Results fit those expected
if risk of intraspecific interactions in such a solitary predator was arnong the selective
pressures leading to the evolution of communication system
Vacuum energy in Einstein-Gauss-Bonnet AdS gravity
A finite action principle for Einstein-Gauss-Bonnet AdS gravity is presented.
The boundary term, which is different for even and odd dimensions, is a
functional of the boundary metric, intrinsic curvature and extrinsic curvature.
For even dimensions, the boundary term corresponds to the maximal Chern form of
the spacetime, and the asymptotic AdS condition for the curvature suffices for
the well-posedness of this action. For odd dimensions, the action is stationary
under a boundary condition on the variation of the extrinsic curvature. The
background-independent Noether charges associated to asymptotic symmetries are
found and the Euclidean continuation of the action correctly describes the
black hole thermodynamics in the canonical ensemble. In particular, this
procedure leads to a covariant formula for the vacuum energy in odd-dimensional
asymptotically AdS spacetimes.Comment: RevTex, 5 pages, accepted for publication in PR
Hamilton-Jacobi Counterterms for Einstein-Gauss-Bonnet Gravity
The on-shell gravitational action and the boundary stress tensor are
essential ingredients in the study of black hole thermodynamics. We employ the
Hamilton-Jacobi method to calculate the boundary counterterms necessary to
remove the divergences and allow the study of the thermodynamics of
Einstein-Gauss-Bonnet black holes.Comment: 21 pages, LaTe
Thermodynamics of Einstein-Born-Infeld black holes with negative cosmological constant
We study the thermodynamics associated to topological black hole solutions of
AdS gravity coupled to nonlinear electrodynamics (Born-Infeld) in any
dimension, using a background-independent regularization prescription for the
Euclidean action given by boundary terms which explicitly depend on the
extrinsic curvature (Kounterterms series). A finite action principle leads to
the correct definition of thermodynamic variables as Noether charges, which
satisfy a Smarr-like relation. In particular, for the odd-dimensional case, a
consistent thermodynamic description is achieved if the internal energy of the
system includes the vacuum energy for AdS spacetime.Comment: 29 pages, no figures; additional comments on extreme black hole case,
a few references added; final version for PR
Effectively four-dimensional spacetimes emerging from d=5 Einstein-Gauss-Bonnet Gravity
Einstein-Gauss-Bonnet gravity in five-dimensional spacetime provides an
excellent example of a theory that, while including higher-order curvature
corrections to General Relativity, still shares many of its features, such as
second-order field equations for the metric. We focus on the largely unexplored
case where the coupling constants of the theory are such that no
constant-curvature solution is allowed, leaving open the question of what the
vacuum state should then be. We find that even a slight deviation from the
anti-de Sitter Chern-Simons theory, where the vacuum state is five-dimensional
AdS spacetime, leads to a complete symmetry breakdown, with the fifth dimension
either being compactified into a small circle or shrinking away exponentially
with time. A complete family of solutions, including duality relations among
them, is uncovered and shown to be unique within a certain class. This
dynamical dimensional reduction scenario seems particularly attractive as a
means for higher-dimensional theories to make contact with our four-dimensional
world.Comment: 9 pages, 4 figures. v2: New section on geometrical significance of
solutions. Final version for CQ
Thermodynamics of Black Holes in Schroedinger Space
A black hole and a black hyperboloid solutions in the space with the
Schroedinger isometries are presented and their thermodynamics is examined. The
on-shell action is obtained by the difference between the extremal and
non-extremal ones with the unusual matching of the boundary metrics. This
regularization method is first applied to the black brane solution in the space
of the Schroedinger symmetry and shown to correctly reproduce the known
thermodynamics. The actions of the black solutions all turn out to be the same
as the AdS counterparts. The phase diagram of the black hole system is obtained
in the parameter space of the temperature and chemical potential and the
diagram contains the Hawking-Page phase transition and instability lines.Comment: 20 page
Gauss-Bonnet brane-world cosmology without -symmetry
We consider a single 3-brane situated between two bulk spacetimes that posses
the same cosmological constant, but whose metrics do not posses a
-symmetry. On each side of the brane, the bulk is a solution to
Gauss-Bonnet gravity. This asymmetry modifies junction conditions, and so new
terms arise in the Friedmann equation. If these terms become dominant, these
behave cosmological constant at early times for some case, and might remove the
initial singularity for other case. However, we show that these new terms can
not become dominant ones under usual conditions when our brane is outside an
event horizon. We also show that any brane-world scenarios of this type revert
to a -symmetric form at late times, and hence rule out certain proposed
scenarios.Comment: 8 pages, 3 figures; Minor typos corrected. References added. V3:
Numerical errors are corrected. Fig.1 and Fig.3 are replaced. V4: published
versio
Regularization of odd-dimensional AdS gravity: Kounterterms
As an alternative to the Dirichlet counterterms prescription, I introduce the
concept of Kounterterms as the boundary terms with explicit dependence on the
extrinsic curvature K_{ij} that regularize the AdS gravity action. Instead of a
Dirichlet boundary condition on the metric, a suitable choice of the boundary
conditions --compatible with any asymptotically AdS (AAdS) spacetime-- ensures
a finite action principle for all odd dimensions. Background-independent
conserved quantities are obtained as Noether charges associated to asymptotic
symmetries and their general expression appears naturally split in two parts.
The first one gives the correct mass and angular momentum for AAdS black
holes and vanishes identically for globally AdS spacetimes. Thus, the second
part is a covariant formula for the vacuum energy in AAdS spacetimes and
reproduces the results obtained by the Dirichlet counterterms method in a
number of cases. It is also shown that this Kounterterms series regularizes the
Euclidean action and recovers the correct black hole thermodynamics in odd
dimensions.Comment: 35+6 pages, 8 references and an appendix added, improved discussion
on boundary conditions and geometrical origin of Kounterterms. Version
accepted in JHE
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