80 research outputs found
The effect of Pressure in Higher Dimensional Quasi-Spherical Gravitational Collapse
We study gravitational collapse in higher dimensional quasi-spherical
Szekeres space-time for matter with anisotropic pressure. Both local and global
visibility of central curvature singularity has been studied and it is found
that with proper choice of initial data it is possible to show the validity of
CCC for six and higher dimensions. Also the role of pressure in the collapsing
process has been discussed.Comment: 11 pages, 6 figures, RevTeX styl
Shell Crossing Singularities in Quasi-Spherical Szekeres Models
We investigate the occurrence of shell crossing singularities in
quasi-spherical Szekeres dust models with or without a cosmological constant.
We study the conditions for shell crossing singularity both from physical and
geometrical point of view and they are in agreement.Comment: 10 latex pages, RevTex style, no figure
Collapse Dynamics of a Star of Dark Matter and Dark Energy
In this work, we study the collapse dynamics of an inhomogeneous spherically
symmetric star made of dark matter (DM) and dark energy (DE). The dark matter
is taken in the form of a dust cloud while anisotropic fluid is chosen as the
candidate for dark energy. It is investigated how dark energy modifies the
collapsing process and is examined whether dark energy has any effect on the
Cosmic Censorship Conjecture. The collapsing star is assumed to be of finite
radius and the space time is divided into three distinct regions and
, where represents the boundary of the star and
denotes the interior (exterior) of the star. The junction
conditions for matching over are specified. Role of Dark
energy in the formation of apparent horizon is studied and central singularity
is analyzed.Comment: 13 page
Naked Singularities in Higher Dimensional Szekeres Space-time
In this paper we study the quasi-spherical gravitational collapse of (n+2)
dimensional Szekeres space-time. The nature of the central shell focusing
singularity so formed is analyzed by studying both the radial null and
time-like geodesic originated from it. We follow the approach of Barve et al to
analyze the null geodesic and find naked singularity in different situations.Comment: 11 Latex Pages, 4 figures, RevTex styl
Emergent Universe with Exotic Matter in Brane World Scenario
In this work, we have examined the emergent scenario in brane world model for
phantom and tachyonic matter. For tachyonic matter field we have obtained
emergent scenario is possible for closed, open and at model of the universe
with some restriction of potential. For normal scalar field the emergent
scenario is possible only for closed model and the result is identical with the
work of Ellis et al [2], but for phantom field the emergent scenario is
possible for closed, open and at model of the universe with some restriction of
potential
Higher Dimensional Cosmology with Some Dark Energy Models in Emergent, Logamediate and Intermediate Scenarios of the Universe
We have considered N-dimensional Einstein field equations in which
four-dimensional space-time is described by a FRW metric and that of extra
dimensions by an Euclidean metric. We have chosen the exponential forms of
scale factors a and d numbers of b in such a way that there is no singularity
for evolution of the higher dimensional Universe. We have supposed that the
Universe is filled with K-essence, Tachyonic, Normal Scalar Field and
DBI-essence. Here we have found the nature of potential of different scalar
field and graphically analyzed the potentials and the fields for three scenario
namely Emergent Scenario, Logamediate Scenario and Intermediate Scenario. Also
graphically we have depicted the geometrical parameters named statefinder
parameters and slow-roll parameters in the higher dimensional cosmology with
the above mentioned scenarios.Comment: 21 pages, 36 figure
A New Variable Modified Chaplygin Gas Model Interacting with Scalar Field
In this letter we present a new form of the well known Chaplygin gas model by
introducing inhomogeneity in the EOS. This model explains crossing.
Also we have given a graphical representation of the model using
parameters. We have also considered an interaction of this model with the
scalar field by introducing a phenomenological coupling function and have shown
that the potential decays with time.Comment: 7 pages, 3 figure
Brane world solutions of perfect fluid in the background of a bulk containing dust or cosmological constant
The paper presents some solutions to the five dimensional Einstein equations
due to a perfect fluid on the brane with pure dust filling the entire bulk in
one case and a cosmological constant (or vacuum) in the bulk for the second
case. In the first case, there is a linear relationship between isotropic
pressure, energy density and the brane tension, while in the second case, the
perfect fluid is assumed to be in the form of chaplygin gas. Cosmological
solutions are found both for brane and bulk scenarios and some interesting
features are obtained for the chaplygin gas on the brane which are distinctly
different from the standard cosmology in four dimensions.Comment: 10 Latex pages, 5 figure
Accretions of Various Types of Dark Energies onto Morris-Thorne Wormhole
In this work, we have studied accretion of the dark energies onto
Morris-Thorne wormhole. For quintessence like dark energy, the mass of the
wormhole decreases and phantom like dark energy, the mass of wormhole
increases. We have assumed two types of dark energy like variable modified
Chaplygin gas (VMCG) and generalized cosmic Chaplygin gas (GCCG). We have found
the expression of wormhole mass in both cases. We have found the mass of the
wormhole at late universe and this is finite. For our choices the parameters
and the function , these models generate only quintessence dark energy
(not phantom) and so wormhole mass decreases during evolution of the universe.
Next we have assumed 5 kinds of parametrizations of well known dark energy
models. These models generate both quintessence and phantom scenarios. So if
these dark energies accrete onto the wormhole, then for quintessence stage,
wormhole mass decreases upto a certain value (finite value) and then again
increases to infinite value for phantom stage during whole evolution of the
universe. We also shown these results graphically.Comment: 9 pages, 7 figures. arXiv admin note: text overlap with
arXiv:1112.615
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