7 research outputs found
Quintom dark energy in DGP braneworld cosmology
In this paper we consider a symmetrical 3-brane embedded in a
5-dimensional spacetime. We study the effective Einstein equation and
acceleration condition in presence of the quintom dark energy fluid as the bulk
matter field. It is shown that the time-dependent bulk quintom field induces a
time-dependent cosmological constant on the brane. In the framework of the DGP
model, the effective Einstein equation is obtained in two different cases: i)
where the quintom field is considered as the bulk matter field and the brane is
empty and, ii) where the quintom dark energy is confined on the brane and the
bulk is empty. We show that in both cases one could obtain a self-inflationary
solution at late time in positive branch , and an asymptotically
static universe in negative branch .Comment: 12 pages, 8 figure
Holographic Chaplygin gas model
In this paper we consider a correspondence between the holographic dark
energy density and Chaplygin gas energy density in FRW universe. Then we
reconstruct the potential and the dynamics of the scalar field which describe
the Chaplygin cosmology.Comment: 9 pages, no figure
Interacting holographic dark energy model in non-flat universe
We employ the holographic model of interacting dark energy to obtain the
equation of state for the holographic energy density in non-flat (closed)
universe enclosed by the event horizon measured from the sphere of horizon
named .Comment: 8 pages, the address of author changed, some references adde
The holographic dark energy in non-flat Brans-Dicke cosmology
In this paper we study cosmological application of holographic dark energy
density in the Brans-Dicke framework. We employ the holographic model of dark
energy to obtain the equation of state for the holographic energy density in
non-flat (closed) universe enclosed by the event horizon measured from the
sphere of horizon named . Our calculation show, taking
for the present time, the lower bound of is -0.9. Therefore it is impossible to have
crossing -1. This implies that one can not generate phantom-like equation of
state from a holographic dark energy model in non-flat universe in the
Brans-Dicke cosmology framework. In the other hand, we suggest a correspondence
between the holographic dark energy scenario in flat universe and the phantom
dark energy model in framework of Brans-Dicke theory with potential.Comment: 10 pages, no figures, abstract and text extended, references adde
Interacting holographic generalized Chaplygin gas model
In this paper we consider a correspondence between the holographic dark
energy density and interacting generalized Chaplygin gas energy density in FRW
universe. Then we reconstruct the potential of the scalar field which describe
the generalized Chaplygin cosmology.Comment: 12 pages, no figur
String or M theory axion as a quintessence
A slow-rolling scalar field ( Quintessence) with potential energy
has been proposed as the origin of
accelerating universe at present. We investigate the effective potential of
in the framework of supergravity model including the quantum corrections
induced by generic (nonrenormalizable) couplings of to the gauge and
charged matter multiplets. It is argued that the K\"ahler potential,
superpotential and gauge kinetic functions of the underlying supergravity model
are required to be invariant under the variation of with an extremely fine
accuracy in order to provide a working quintessence potential. Applying these
results for string or -theory, we point out that the heterotic -theory or
Type I string axion can be a plausible candidate for quintessence if (i) it
does not couple to the instanton number of gauge interactions not weaker than
those of the standard model and (ii) the modulus partner of the
periodic quintessence axion has a large VEV:
. It is stressed
that such a large gives the gauge unification scale at around the
phenomenologically favored value GeV. To provide an
accelerating universe, the quintessence axion should be at near the top of its
effective potential at present, which requires a severe fine tuning of the
initial condition of and in the early universe. We discuss a late
time inflation scenario based on the modular and CP invariance of the moduli
effective potential, yielding the required initial condition in a natural
manner if the K\"ahler metric of the quintessence axion superfield receives a
sizable nonperturbative contribution.Comment: 23 pages, 3 figures, version to be published at Phys. Rev.