2,988 research outputs found
Entropy Function and Universality of Entropy-Area Relation for Small Black Holes
We discuss the entropy-area relation for the small black holes with higher
curvature corrections by using the entropy function formalism and field
redefinition method. We show that the entropy of small black hole is
proportional to its horizon area . In particular we find a universal result
that , the ratio is two times of Bekenstein-Hawking entropy-area
formula in many cases of physical interest. In four dimensions, the universal
relation is always true irrespective of the coefficients of the higher-order
terms if the dilaton couplings are the same, which is the case for string
effective theory, while in five dimensions, the relation again holds
irrespective of the overall coefficient if the higher-order corrections are in
the GB combination. We also discuss how this result generalizes to known
physically interesting cases with Lovelock correction terms in various
dimensions, and possible implications of the universal relation.Comment: minor corrections, a ref. adde
Thermodynamics of Dual CFTs for Kerr-AdS Black Holes
Recently Gibbons {\it et al.} in hep-th/0408217 defined a set of conserved
quantities for Kerr-AdS black holes with the maximal number of rotation
parameters in arbitrary dimension. This set of conserved quantities is defined
with respect to a frame which is non-rotating at infinity. On the other hand,
there is another set of conserved quantities for Kerr-AdS black holes, defined
by Hawking {\it et al.} in hep-th/9811056, which is measured relative to a
frame rotating at infinity. Gibbons {\it et al.} explicitly showed that the
quantities defined by them satisfy the first law of black hole thermodynamics,
while those quantities defined by Hawking {\it et al.} do not obey the first
law. In this paper we discuss thermodynamics of dual CFTs to the Kerr-AdS black
holes by mapping the bulk thermodynamic quantities to the boundary of the AdS
space. We find that thermodynamic quantities of dual CFTs satisfy the first law
of thermodynamics and Cardy-Verlinde formula only when these thermodynamic
quantities result from the set of bulk quantities given by Hawking {\it et
al.}. We discuss the implication of our results.Comment: Revtex4, twocolumn, 6 pages, v2: 7 pages, more references and
comments added, an err correcte
Spinor Dark Energy and Cosmological Coincidence Problem
Recently, the so-called Elko spinor field has been proposed to be a candidate
of dark energy. It is a non-standard spinor and has unusual properties. When
the Elko spinor field is used in cosmology, its unusual properties could bring
some interesting consequences. In the present work, we discuss the cosmological
coincidence problem in the spinor dark energy models by using the dynamical
system method. Our results show that the cosmological coincidence problem
should be taken to heart in the investigations of spinor dark energy models.Comment: 9 pages, revtex4; v2: major revision, title changed, Phys. Lett. B in
press; v3: published versio
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