6 research outputs found
Restoring New Agegraphic Dark Energy in RS II Braneworld
Motivated by recent works [1,2], we investigate new agegraphic model of dark
energy in the framework of RS II braneworld. We also include the case of
variable gravitational constant in our model. Furthermore, we establish
correspondence between the new agegraphic dark energy with other dark energy
candidates based on scalar fields.Comment: 13 pages, accepted for publication in IJT
Bianchi {VI} in Scalar and Scalar-Tensor Cosmologies
We study several cosmological models with Bianchi \textrm{VI}
symmetries under the self-similar approach. In order to study how the
\textquotedblleft constants\textquotedblright\ and may vary, we
propose three scenarios where such constants are considered as time functions.
The first model is a perfect fluid. We find that the behavior of and
are related. If behaves as a growing time function then
is a positive decreasing time function but if is decreasing then
is negative. For this model we have found a new solution. The second model is a
scalar field, where in a phenomenological way, we consider a modification of
the Klein-Gordon equation in order to take into account the variation of .
Our third scenario is a scalar-tensor model. We find three solutions for this
models where is growing, constant or decreasing and is a positive
decreasing function or vanishes. We put special emphasis on calculating the
curvature invariants in order to see if the solutions isotropize.Comment: Typos corrected. References added, minor corrections. arXiv admin
note: text overlap with arXiv:0905.247
Generalized Self-similar Scalar-Tensor Theories
We study through symmetry principles the form of the functions in the
generalizated scalar-tensor theories under the self-similar hypothesis. The
results obtained are absolutely general and valid for all the Bianchi models
and the flat FRW one. We study the concrete example of the Kantowsky-Sach model
finding some exact self-similar solutions.Comment: 21 pages. Typos corrected. References added, minor correction
Holographic dark energy with time depend gravitational constant in the non-flat Hoava-Lifshitz cosmology
We study the holographic dark energy on the subject of
Hoava-Lifshitz gravity with a time dependent gravitational constant
(G(t)), in the non-flat space-time. We obtain the differential equation that
specify the evolution of the dark energy density parameter based on varying
gravitational constant. we find out a relation for the state parameter of the
dark energy equation to low redshifts which containing varying correction.Comment: 11 page
Holographic Dark Energy in Braneworld Models with Moving Branes and the w=-1 Crossing
We apply the bulk holographic dark energy in general 5D two-brane models. We
extract the Friedmann equation on the physical brane and we show that in the
general moving-brane case the effective 4D holographic dark energy behaves as a
quintom for a large parameter-space area of a simple solution subclass. We find
that was larger than -1 in the past while its present value is
, and the phantom bound was crossed
at , a result in agreement with observations. Such a behavior
arises naturally, without the inclusion of special fields or potential terms,
but a fine-tuning between the 4D Planck mass and the brane tension has to be
imposed.Comment: 15 pages, 2 figures, version published in JCA