435 research outputs found
Thermodynamics of Chaplygin gas
We clarify thermodynamics of the Chaplygin gas by introducing the
integrability condition. All thermal quantities are derived as functions of
either volume or temperature. Importantly, we find a new general equation of
state, describing the Chaplygin gas completely. We confirm that the Chaplygin
gas could show a unified picture of dark matter and energy which cools down
through the universe expansion without any critical point (phase transition).Comment: 5 pages, 4 figures, version "Accepted for publication in Astrophysics
& Space Science
Slowly rotating black holes in the Horava-Lifshitz gravity
We investigate slowly rotating black holes in the Ho\v{r}ava-Lifshitz (HL)
gravity. For and , we find a slowly rotating black
hole of the Kehagias-Sfetsos solution in asymptotically flat spacetimes. We
discuss their thermodynamic properties by computing mass, temperature, angular
momentum, and angular velocity on the horizon.Comment: 12 pages, no figures, version to appear in EPJ
Quasinormal modes and hidden conformal symmetry in the Reissner-Nordstrom black hole
It is shown that the scalar wave equation in the near-horizon limit respects
a hidden SL(2,R) invariance in the Reissner-Nordstrom (RN) black hole
spacetimes. We use the SL(2,R) symmetry to determine algebraically the purely
imaginary quasinormal frequencies of the RN black hole. We confirm that these
are exactly quasinormal modes of scalar perturbation around the near-extremal
black hole.Comment: 17 pages, 1 figure, version to appear in EPJ
Entropic force and its cosmological implications
We investigate a possibility of realizing the entropic force into the
cosmology. A main issue is how the holographic screen is implemented in the
Newtonian cosmology. Contrary to the relativistic realization of Friedmann
equations, we do not clarify the connection between Newtonian cosmology and
entropic force because there is no way of implementing the holographic screen
in the Newtonian cosmology.Comment: 16 pages, no figures, version "Accepted for publication in
Astrophysics & Space Science
Phase transitions for the Lifshitz black holes
We study possibility of phase transitions between Lifshitz black holes and
other configurations by using free energies explicitly. A phase transition
between Lifshitz soliton and Lifshitz black hole might not occur in three
dimensions. We find that a phase transition between Lifshitz and BTZ black
holes unlikely occurs because they have different asymptotes. Similarly, we
point out that any phase transition between Lifshitz and black branes unlikely
occurs in four dimensions since they have different asymptotes. This is
consistent with a necessary condition for taking a phase transition in the
gravitational system, which requires the same asymptote.Comment: 19 pages, 7 figures, a revised version to appear in EPJ
The absence of the Kerr black hole in the Ho\v{r}ava-Lifshitz gravity
We show that the Kerr metric does not exist as a fully rotating black hole
solution to the modified Ho\v{r}ava-Lifshitz (HL) gravity with
and case. We perform it by showing that the Kerr metric does not
satisfy full equations derived from the modified HL gravity.Comment: 35 pages, no figure
Regular black hole in three dimensions
We find a new black hole in three dimensional anti-de Sitter space by
introducing an anisotropic perfect fluid inspired by the noncommutative black
hole. This is a regular black hole with two horizons. We compare thermodynamics
of this black hole with that of non-rotating BTZ black hole. The first-law of
thermodynamics is not compatible with the Bekenstein-Hawking entropy.Comment: 15 pages, 16 figures, 3D noncommutative black hole included as Sec 4,
a version to appear in EPJ
Nonpropagation of massive mode on AdS2 in topologically massive gravity
Making use of Achucarro-Ortiz (AO) type of dimensional reduction, we study
the topologically massive gravity with a negative cosmological constant on AdS2
spacetimes. For a constant dilaton, this two-dimensional model also admits
three AdS2 vacuum solutions, which are related to two AdS3 and warped AdS3
backgrounds with an identification upon uplifting three dimensions. We carry
out the perturbation analysis around these backgrounds to find what is a
physically propagating field. However, it turns out that there is no
propagating massive mode on AdS2 background, in contrast to the Kaluza-Klein
(KK) type of dimensional reduction. We note that two dimensionally reduced
actions are different and thus, the non-equivalence of their on-shell
amplitudes is obtained.Comment: 19 pages, version to appear in EPJ
Dilaton gravity approach to three dimensional Lifshitz black hole
The z=3 Lifshitz black hole is an exact black hole solution to the new
massive gravity in three dimensions. In order to understand this black hole
clearly, we perform a dimensional reduction to two dimensional dilaton gravity
by utilizing the circular symmetry. Considering the linear dilaton, we find the
same Lifshitz black hole in two dimensions. This implies that all thermodynamic
quantities of the z=3 Lifshitz black hole could be obtained from its
corresponding black hole in two dimensions. As a result, we derive the
temperature, mass, heat capacity, Bekesnstein-Hawking entropy, and free energy.Comment: 13 pages, 1 figure, version to appear in EPJ
Does entropic force always imply the Newtonian force law?
We study the entropic force by introducing a bound between
entropy and area which was derived by imposing the non-gravitational collapse
condition. In this case, applying a modified entropic force to this system does
not lead to the Newtonian force law.Comment: 11 pages, version to appear in EPJ
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