1,316 research outputs found
Phantom Accretion by Five Dimensional Charged Black Hole
This paper deals with the dynamical behavior of phantom field near five
dimensional charged black hole. We formulate equations of motion for
steady-state spherically symmetric flow of phantom fluids. It is found that
phantom energy accretes onto black holes for . Further, the location of
critical point of accretion are evaluated that leads to mass to charge ratio
for 5D charged black hole. This ratio implies that accretion cannot transform a
black hole into a naked singularity. We would like to mention here that this
work is an irreducible extension of 4D charged black hole.Comment: 8 pages, accepted for publication in Mod. Phys. Lett.
Reconstructing the potentials for the quintessence and tachyon dark energy, from the holographic principle
We propose an holographic quintessence and tachyon models of dark energy. The
correspondence between the quintessence and tachyon energy densities with the
holographic density, allows the reconstruction of the potentials and the
dynamics for the quintessence and tachyon fields, in flat FRW background. The
proposed infrared cut-off for the holographic energy density works for two
cases of the constant : for we reconstructed the holographic
quintessence model in the region before the crossing for the EoS
parameter. The cosmological dynamics for was also reconstructed for
the holographic quintessence and tachyon models.Comment: 21 pages, 18 figures, 2 table
Induced cosmological constant and other features of asymmetric brane embedding
We investigate the cosmological properties of an "induced gravity" brane
scenario in the absence of mirror symmetry with respect to the brane. We find
that brane evolution can proceed along one of four distinct branches. By
contrast, when mirror symmetry is imposed, only two branches exist, one of
which represents the self-accelerating brane, while the other is the so-called
normal branch. This model incorporates many of the well-known possibilities of
brane cosmology including phantom acceleration (w < -1), self-acceleration,
transient acceleration, quiescent singularities, and cosmic mimicry.
Significantly, the absence of mirror symmetry also provides an interesting way
of inducing a sufficiently small cosmological constant on the brane. A small
(positive) Lambda-term in this case is induced by a small asymmetry in the
values of bulk fundamental constants on the two sides of the brane.Comment: 17 pages, 4 figures. New results and two figures discussing transient
acceleration are included. Version accepted for publication in JCA
Solutions to CDM Universe Derived from Global Brane Model
An exact solution of brane universe is studied and the result indicates that
Friedmann equations on the brane are modified with an extra term. This term can
play the role of dark energy and make the universe accelerate. In order to
derive the CDM Universe from this global brane model, the new
solutions are obtained to describe the manifold.Comment: 7 pages, no figure, accepted by MPL
Brane Universes and the Cosmological Constant
The cosmological constant problem and brane universes are reviewed briefly.
We discuss how the cosmological constant problem manifests itself in various
scenarios for brane universes. We review attempts - and their difficulties -
that aim at a solution of the cosmological constant problem.Comment: corrected typos, added references, 13 pages, accepted by MPLA as
brief revie
Transition from quintessence to phantom phase in quintom model
Assuming the Hubble parameter is a continuous and differentiable function of
comoving time, we investigate necessary conditions for quintessence to phantom
phase transition in quintom model. For power-law and exponential potential
examples, we study the behavior of dynamical dark energy fields and Hubble
parameter near the transition time, and show that the phantom-divide-line w=-1
is crossed in these models.Comment: LaTeX, 19 pages, four figures, some minor changes in Introduction,
two figures added and the references updated, accepted for publication in
Phys. Rev.
Reconstruction of Scalar Potentials in Induced Gravity and Cosmology
We develop a technique for the reconstruction of the potential for a scalar
field in cosmological models based on induced gravity. The potentials
reproducing cosmological evolutions driven by barotropic perfect fluids, a
cosmological constant, a Chaplygin gas and a modified Chaplygin gas are
constructed explicitly.Comment: 14 pages, no figures. Final version published in PL
Program Application Page Web Browser to Display Using the Internet in Delphi 5
The Internet is an unlimited source of information, information on the Internet arepresented in various forms. One form of information available on the Internet is theWorld Wide Web (WWW). WWW is a form of multimedia information preparedusing language that is Hypertaxt Markup Language (HTML).To access the WWW needed a web browser. Web Browser works as a client Dimanclient requested a file from a server in the form of HTML and also displaysinformation to the desktop in the form of multimedia.To create a Web Browser needed an object-oriented programming language calledObject Oriented Program (OOP). One of these programming languages are Delphi 5.With Delphi 5 is very possible someone can make a web browser, since Delphi 5support in the Internet-based programming
The Integrated Sachs-Wolfe Effect in Time Varying Vacuum Model
The integrated Sachs-Wolfe (ISW) effect is an important implication for dark
energy. In this paper, we have calculated the power spectrum of the ISW effect
in the time varying vacuum cosmological model, where the model parameter
is obtained by the observational constraint of the growth rate.
It's found that the source of the ISW effect is not only affected by the
different evolutions of the Hubble function and the dimensionless matter
density , but also by the different growth function , all
of which are changed due to the presence of matter production term in the time
varying vacuum model. However, the difference of the ISW effect in
model and model is lessened to
a certain extent due to the integration from the time of last scattering to the
present. It's implied that the observations of the galaxies with high redshift
are required to distinguish the two models
- …