313 research outputs found
Generalized second law and entropy bound for a Reissner- Nordstr\"om black hole
It has been conjectured that black hole interacting with its surroundings
will obey the Generalized Second Law () of thermodynamics. Conservation of
is due to the fully thermal nature of Hawking radiation and an upper
bound on entropy. We study these aspects for a
Reissner-Nordstrm ()black hole and conjecture that
may be conserved if the equation of state of radiation near the horizon is
modified. An upper bound on , similar to the Bekenstein form evolves in
the calculation.Comment: 11 page
Thermodynamics and Spectroscopy of charged Dilaton black holes
The Bohr-Sommerfeld quantization rule is useful to study the area spectrum of
black holes by employing adiabatic invariants. This method is extended to
charged dilaton black holes in 2+1 dimensions. We put the background space-time
into the Kruskal-like coordinate to find the period with respect to Euclidian
time. Also assuming that the adiabatic invariant obeys Bohr-Sommerfeld
quantization rule, detailed study of area and entropy spectrum has been done.
It is dependent on the charge and is equally spaced as well.
We also investigate the thermodynamics of the charged dilaton black hole.Comment: 10 pages and 3 figures; accepted in "General Relativity and
Gravitation"(GRG). arXiv admin note: text overlap with arXiv:1204.1786,
arXiv:1203.5947 by other author
Dirac Quasinormal modes of MSW black holes
In this paper we study the Dirac quasinormal modes of an uncharged 2 + 1
black hole proposed by Mandal et. al and referred to as MSW black hole in this
work. The quasi- normal mode is studied using WKB approximation method. The
study shows that the imaginary part of quasinormal frequencies increases
indicating that the oscillations are damping and hence the black hole is stable
against Dirac perturbations.Comment: 8 page, 3 figure, Appear in MPL
Absorption cross section of RN black hole
The behavior of a charged scalar field in the RN black hole space time is
studied using WKB approximation. In the present work it is assumed that matter
waves can get reflected from the event horizon. Using this effect, the Hawking
temperature and the absorption cross section for RN black hole placed in a
charged scalar field are calculated. The absorption cross section is found to be inversely proportional to square of the Hawking
temperature of the black hole.Comment: 6 pages, 2 figure
First Order Phase Transitions in a Bianchi type-I universe
Considering the theory of induced gravity coupled to matter fields, taking
the interaction potential model we evaluate the one-loop effective
potential in a (3+1)dimensional Bianchi type-I spacetime. It is proved that the
theory can be regularised in (3+1)dimensional curved spacetime. We
evaluate the finite temperature effective potential and study the temperature
dependence of phase transitions. The nature of phase transitions in the early
universe is clarified to be of first order. The effects of spacetime curvature
and arbitrary field coupling on the phase transitions in the early universe are
also discussed.Comment: 20 pages, 7 figures, To appear in Physical Rev.
Area spectrum and thermodynamics of KS black holes in Ho\v{r}ava gravity
We investigate the area spectrum of Kehagias-Sfetsos black hole in
Ho\v{r}ava-Lifshitz gravity via modified adiabatic invariant and Bohr-Sommerfeld quantization rule. We find that the area spectrum is
equally spaced with a spacing of . We have also studied
the thermodynamic behavior of KS black hole by deriving different thermodynamic
quantities.Comment: 9 pages, 3 figures. Gen Relativ Gravit 201
Late-time evolution of Dirac field around Schwarzschild-quintessence black hole
The late-time evolution of Dirac field around spherically symmetric black
hole surrounded by quintessece is studied numerically. Our results show, for
lower values of the quintessence state parameter \epsilon, Dirac field decays
as power-law tail but with a slower decay rate than the corresponding
Schwarzschild case. But for \epsilon<-1/3, all the \ell-poles of the Dirac
field give up the power-law decay form and relax to a constant residual field
at asymptotically late times. The value of this residual field for which the
field settles down varies on different surfaces. It has the lowest value on the
black hole event horizon, increases as the radial distance increases and
maximizes on the cosmological horizon.Comment: 10 pages, 5 figures. To appear in MPLA. arXiv admin note: text
overlap with arXiv:1210.047
Data Analysis of Massive Gravitational Waves from Gamma Ray Bursts
We investigate the detectability of massive mode of polarization of
Gravitational Waves (GWs) in f(R) theory of gravity associated with Gamma Ray
Bursts (GRBs) sources. We obtain the beam pattern function of Laser
Interferometric Gravitational wave Observatory (LIGO) corresponding to the
massive polarization of GWs and perform Bayesian analysis to study this
polarization. It is found that the massive polarization component with a mass
of 10^-22eV/c2 is too weak to be detected at LIGO with its current
configuration.Comment: 17 pages, 4 figures, 2 tables, 51 references Accepted for publication
in International Journal of Modern Physics
A Mond Programme from Einstein Hilbert Action
In the usual derivation of Einstein's equation from action, the surface terms
are neglected. Hawking \cite{hw} gave a derivation of the gravitational
Hamiltonian keeping all surface terms. Using such surface terms Easson
et.al.\cite{ea} showed that Friedmann equation could get modified and using the
modified Friedmann equation they could explain the cosmic acceleration. We
study the effect of surface terms on a galactic scale and find that the
classical limit of the modified Friedmann equation will lead to a MOND like
acceleration term.Comment: 5 page
Late time tails of fields around Schwarzschild black hole surrounded by quintessence
The evolution of scalar, electromagnetic and gravitational fields around
spherically symmetric black hole surrounded by quintessence are studied with
special interest on the late-time behavior. In the ring down stage of
evolution, we find in the evolution picture that the fields decay more slowly
due to the presence of quintessence. As the quintessence parameter \epsilon
decreases, the decay of l=0 mode of scalar field gives up the power-law form of
decay and relaxes to a constant residual field at asymptotically late times.
The l>0 modes of scalar, electromagnetic and gravitational fields show a
power-law decay for large values of \epsilon, but for smaller values of
\epsilon they give way to an exponential decay.Comment: 15 pages, 13 figures. Accepted for publication in Gen. Relativ. Gra
- …