2,797 research outputs found
Black Holes in Gravity with Conformal Anomaly and Logarithmic Term in Black Hole Entropy
We present a class of exact analytic and static, spherically symmetric black
hole solutions in the semi-classical Einstein equations with Weyl anomaly. The
solutions have two branches, one is asymptotically flat and the other
asymptotically de Sitter. We study thermodynamic properties of the black hole
solutions and find that there exists a logarithmic correction to the well-known
Bekenstein-Hawking area entropy. The logarithmic term might come from non-local
terms in the effective action of gravity theories. The appearance of the
logarithmic term in the gravity side is quite important in the sense that with
this term one is able to compare black hole entropy up to the subleading order,
in the gravity side and in the microscopic statistical interpretation side.Comment: Revtex, 10 pages. v2: minor changes and to appear in JHE
Lovelock gravity from entropic force
In this paper, we first generalize the formulation of entropic gravity to
(n+1)-dimensional spacetime. Then, we propose an entropic origin for
Gauss-Bonnet gravity and more general Lovelock gravity in arbitrary dimensions.
As a result, we are able to derive Newton's law of gravitation as well as the
corresponding Friedmann equations in these gravity theories. This procedure
naturally leads to a derivation of the higher dimensional gravitational
coupling constant of Friedmann/Einstein equation which is in complete agreement
with the results obtained by comparing the weak field limit of Einstein
equation with Poisson equation in higher dimensions. Our study shows that the
approach presented here is powerful enough to derive the gravitational field
equations in any gravity theory. PACS: 04.20.Cv, 04.50.-h, 04.70.Dy.Comment: 10 pages, new versio
Fourth clivar workshop on the evaluation of ENSO processes in climate models: ENSO in a changing climate
n/aThe organizers acknowledge the generous support of the World Climate Research Programme/CLIVAR, the Centre National de la Recherche Scientifique–Institut National des Sciences de l’Univers (CNRS-INSU), the LabEx L-IPSL, and Sorbonne Universités and wish to thank Lei Han, from the International CLIVAR Global Project Office in Qingdao, China, for his invaluable help in organizing this workshop
Effects of Krill Oil on serum lipids of hyperlipidemic rats and human SW480 cells
© 2008 Zhu et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Deformation of Codimension-2 Surface and Horizon Thermodynamics
The deformation equation of a spacelike submanifold with an arbitrary
codimension is given by a general construction without using local frames. In
the case of codimension-1, this equation reduces to the evolution equation of
the extrinsic curvature of a spacelike hypersurface. In the more interesting
case of codimension-2, after selecting a local null frame, this deformation
equation reduces to the well known (cross) focusing equations. We show how the
thermodynamics of trapping horizons is related to these deformation equations
in two different formalisms: with and without introducing quasilocal energy. In
the formalism with the quasilocal energy, the Hawking mass in four dimension is
generalized to higher dimension, and it is found that the deformation of this
energy inside a marginal surface can be also decomposed into the contributions
from matter fields and gravitational radiation as in the four dimension. In the
formalism without the quasilocal energy, we generalize the definition of slowly
evolving future outer trapping horizons proposed by Booth to past trapping
horizons. The dynamics of the trapping horizons in FLRW universe is given as an
example. Especially, the slowly evolving past trapping horizon in the FLRW
universe has close relation to the scenario of slow-roll inflation. Up to the
second order of the slowly evolving parameter in this generalization, the
temperature (surface gravity) associated with the slowly evolving trapping
horizon in the FLRW universe is essentially the same as the one defined by
using the quasilocal energy.Comment: Latex, 61 pages, no figures; v2, type errors corrected; v3,
references and comments are added, English is improved, to appear in JHE
On Charged Lifshitz Black Holes
We obtain exact solutions of charged asymptotically Lifshitz black holes in
arbitrary (d+2) dimensions, generalizing the four dimensional solution
investigated in 0908.2611[hep-th]. We find that both the conventional
Hamiltonian approach and the recently proposed method for defining mass in
non-relativistic backgrounds do not work for this specific example. Thus the
mass of the black hole can only be determined by the first law of
thermodynamics. We also obtain perturbative solutions in five-dimensional
Gauss-Bonnet gravity. The ratio of shear viscosity over entropy density and the
DC conductivity are calculated in the presence of Gauss-Bonnet corrections.Comment: 24 pages, no figures, to appear in JHE
Thermodynamics of a class of non-asymptotically flat black holes in Einstein-Maxwell-Dilaton theory
We analyse in detail the thermodynamics in the canonical and grand canonical
ensembles of a class of non-asymptotically flat black holes of the
Einstein-(anti) Maxwell-(anti) Dilaton theory in 4D with spherical symmetry. We
present the first law of thermodynamics, the thermodynamic analysis of the
system through the geometrothermodynamics methods, Weinhold, Ruppeiner,
Liu-Lu-Luo-Shao and the most common, that made by the specific heat. The
geometric methods show a curvature scalar identically zero, which is
incompatible with the results of the analysis made by the non null specific
heat, which shows that the system is thermodynamically interacting, does not
possess extreme case nor phase transition. We also analyse the local and global
stability of the thermodynamic system, and obtain a local and global stability
for the normal case for 0<\gamma<1 and for other values of \gamma, an unstable
system. The solution where \gamma=0 separates the class of locally and globally
stable solutions from the unstable ones.Comment: 18 pages, version accepted for publication in General Relativity and
Gravitatio
Thermodynamic analysis of black hole solutions in gravitating nonlinear electrodynamics
We perform a general study of the thermodynamic properties of static
electrically charged black hole solutions of nonlinear electrodynamics
minimally coupled to gravitation in three space dimensions. The Lagrangian
densities governing the dynamics of these models in flat space are defined as
arbitrary functions of the gauge field invariants, constrained by some
requirements for physical admissibility. The exhaustive classification of these
theories in flat space, in terms of the behaviour of the Lagrangian densities
in vacuum and on the boundary of their domain of definition, defines twelve
families of admissible models. When these models are coupled to gravity, the
flat space classification leads to a complete characterization of the
associated sets of gravitating electrostatic spherically symmetric solutions by
their central and asymptotic behaviours. We focus on nine of these families,
which support asymptotically Schwarzschild-like black hole configurations, for
which the thermodynamic analysis is possible and pertinent. In this way, the
thermodynamic laws are extended to the sets of black hole solutions of these
families, for which the generic behaviours of the relevant state variables are
classified and thoroughly analyzed in terms of the aforementioned boundary
properties of the Lagrangians. Moreover, we find universal scaling laws (which
hold and are the same for all the black hole solutions of models belonging to
any of the nine families) running the thermodynamic variables with the electric
charge and the horizon radius. These scale transformations form a one-parameter
multiplicative group, leading to universal "renormalization group"-like
first-order differential equations. The beams of characteristics of these
equations generate the full set of black hole states associated to any of these
gravitating nonlinear electrodynamics...Comment: 51 single column pages, 19 postscript figures, 2 tables, GRG tex
style; minor corrections added; final version appearing in General Relativity
and Gravitatio
The holographic principle
There is strong evidence that the area of any surface limits the information
content of adjacent spacetime regions, at 10^(69) bits per square meter. We
review the developments that have led to the recognition of this entropy bound,
placing special emphasis on the quantum properties of black holes. The
construction of light-sheets, which associate relevant spacetime regions to any
given surface, is discussed in detail. We explain how the bound is tested and
demonstrate its validity in a wide range of examples.
A universal relation between geometry and information is thus uncovered. It
has yet to be explained. The holographic principle asserts that its origin must
lie in the number of fundamental degrees of freedom involved in a unified
description of spacetime and matter. It must be manifest in an underlying
quantum theory of gravity. We survey some successes and challenges in
implementing the holographic principle.Comment: 52 pages, 10 figures, invited review for Rev. Mod. Phys; v2:
reference adde
Holographic Lovelock Gravities and Black Holes
We study holographic implications of Lovelock gravities in AdS spacetimes.
For a generic Lovelock gravity in arbitrary spacetime dimensions we formulate
the existence condition for asymptotically AdS black holes. We consider small
fluctuations around these black holes and determine the constraint on Lovelock
parameters by demanding causality of the boundary theory. For the case of cubic
Lovelock gravity in seven spacetime dimensions we compute the holographic Weyl
anomaly and determine the three point functions of the stress energy tensor in
the boundary CFT. Remarkably, these correlators happen to satisfy the same
relation as the one imposed by supersymmetry. We then compute the energy flux;
requiring it to be positive is shown to be completely equivalent to requiring
causality of the finite temperature CFT dual to the black hole. These
constraints are not stringent enough to place any positive lower bound on the
value of viscosity. Finally, we conjecture an expression for the energy flux
valid for any Lovelock theory in arbitrary dimensions.Comment: 31 pages, 1 figure, harvmac, references added, calculation of
viscosity/entropy ratio include
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