602 research outputs found
Cosmological Evolution of Interacting New Holographic Dark Energy in Non-flat Universe
We consider the interacting holographic dark energy with new infrared cutoff
(involving Hubble parameter and its derivative) in non-flat universe. In this
context, we obtain the equation of state parameter which evolutes the universe
from vacuum dark energy region towards quintessence region for particular
values of constant parameters. It is found that this model always remains
unstable against small perturbations. Further, we establish the correspondence
of this model having quintessential behavior with quintessence, tachyon,
K-essence and dilaton scalar field models. The dynamics of scalar fields and
potentials indicate accelerated expansion of the universe which is consistent
with the current observations. Finally, we discuss the validity of the
generalized second law of thermodynamics in this scenario.Comment: 21 pages, 13 figure
Dynamical Instability of Shear-free Collapsing Star in Extended Teleparallel Gravity
We study the spherically symmetric collapsing star in terms of dynamical
instability. We take the framework of extended teleparallel gravity with
non-diagonal tetrad, power-law form of model presenting torsion and matter
distribution as non-dissipative anisotropic fluid. The vanishing shear scalar
condition is adopted to search the insights of collapsing star. We apply first
order linear perturbation scheme to metric, matter and functions. The
dynamical equations are formulated under this perturbation scheme to develop
collapsing equation for finding dynamical instability limits in two regimes
such as Newtonian and post-Newtonian. We obtain constraint free solution of
perturbed time dependent part with the help of vanishing shear scalar. The
adiabatic index exhibits the instability ranges through second dynamical
equation which depend on physical quantities such as density, pressure
components, perturbed parts of symmetry of star, etc. We also develop some
constraints on positivity of these quantities and obtain instability ranges to
satisfy the dynamical instability condition.Comment: 21 pages; Accepted in EPJC for publicatio
Accretion onto Some Well-Known Regular Black Holes
In this work, we discuss the accretion onto static spherical symmetric
regular black holes for specific choices of equation of state parameter. The
underlying regular black holes are charged regular black hole using Fermi-Dirac
Distribution, logistic distribution, nonlinear electrodynamics, respectively
and Kehagias-Sftesos asymptotically flat regular black hole. We obtain the
critical radius, critical speed and squared sound speed during the accretion
process near the regular black holes. We also study the behavior of radial
velocity, energy density and rate of change of mass for each regular black
holes.Comment: 25 pages, 7 figures, Accepted for publication in Eur. Phys. J.
Effects of Thermal Fluctuations on Non-minimal Regular Magnetic Black Hole
We analyze the effects of thermal fluctuations on a regular black hole (RBH)
of non-minimal Einstein-Yang-Mill theory with gauge field of magnetic Wu-Yang
type and a cosmological constant. We consider the logarithmic corrected entropy
in order to analyze the thermal fluctuations corresponding to non-minimal RBH
thermodynamics. In this scenario, we develop various important thermodynamical
quantities such as entropy, pressure, specific heats, Gibb's free energy and
Helmothz free energy. We investigate first law of thermodynamics in the
presence of logarithmic corrected entropy and non-minimal RBH. We also discuss
the stability of this RBH using various frameworks such as factor
(comprises of ratio of heat capacities), phase transition, grand canonical
ensemble and canonical ensemble. It is observed that the non-minimal RBH
becomes more globally and locally stable if we increase the value of
cosmological constant.Comment: 20 pages, 5 figure
Tidal Forces in Kiselev Black Hole
The aim of this paper is to examine the tidal forces occurred in Kiselev
black hole surrounded by radiation and dust fluids. It is noted that radial and
angular component of tidal force change the sign between event and Cauchy
horizons. We solve the geodesic deviation equation for radially free falling
bodies toward Kiselev black holes. We explain the geodesic deviation vector
graphically and point out the location of event and Cauchy horizons in it for
specific values of radiation and dust parameter.Comment: 20 pages, 10 figure
Accreting Fluids onto Regular Black Holes Via Hamiltonian Approach
We investigate the accretion of test fluids onto regular black holes such as
Kehagias-Sfetsos black hole and a regular black hole with Dagum Distribution
Function. We analyze the accretion process when different test fluids are
falling onto these regular black holes. The accreting fluid is being classified
through equation of state according to features of regular black holes. The
behavior of fluid flow and the existence of sonic points is being checked for
these regular black holes. It is noted that three velocity depends on critical
points and equation of state parameter on phase space.Comment: 25 pages; 10 Figure
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