551 research outputs found
Gauss-Bonnet Brane Cosmology with Radion Stabilization
We study cosmology in a five-dimensional brane-world with a stabilizing
effective potential for the radion and matter localized on the two branes. We
consider the corrections induced by the Gauss-Bonnet contribution to the total
action performing and expansion around the two possible static solutions up to
second order in the ratio between brane matter energy density and brane
tensions. The Friedmann and acceleration equations on the visible brane are
obtained and discussed.Comment: To be published in Phys.Rev.D, References Adde
Inflation and Reheating in Spontaneously Generated Gravity
Inflation is studied in the context of induced gravity (IG) , where is the Ricci scalar, a scalar field and a
dimensionless constant, and diverse symmetry-breaking potentials
are considered. In particular we compared the predictions for Landau-Ginzburg
(LG) and Coleman-Weinberg (CW) type potentials and their possible
generalizations with the most recent data. We find that large field inflation
generally leads to fewer constraints on the parameters and the shape of the
potential whereas small field inflation is more problematic and, if viable,
implies more constraints, in particular on the parameter . We also
examined the reheating phase and obtained an accurate analytical solution for
the dynamics of inflaton and the Hubble parameter by using a multiple scale
analysis (MSA). The solutions were then used to study the average expansion of
the Universe, the average equation of state for the scalar field and both the
perturbative and resonant decays of the inflaton field.Comment: 15 pages, 10 figures, to be published in Phys. Rev.
Reconstruction of Scalar Potentials in Modified Gravity Models
We employ the superpotential technique for the reconstruction of cosmological
models with a non-minimally coupled scalar field evolving on a spatially flat
Friedmann-Robertson-Walker background. The key point in this method is that the
Hubble parameter is considered as a function of the scalar field and this
allows one to reconstruct the scalar field potential and determine the dynamics
of the field itself, without a priori fixing the Hubble parameter as a function
of time or of the scale factor. The scalar field potentials that lead to de
Sitter or asymptotic de Sitter solutions, and those that reproduce the
cosmological evolution given by Einstein-Hilbert action plus a barotropic
perfect fluid, have been obtained.Comment: 12 pages, 2 figures, accepted for publication in PR
Second order brane cosmology with radion stabilization
We study cosmology in the five-dimensional Randall-Sundrum brane-world with a
stabilizing effective potential for the radion and matter localized on the
branes. The analysis is performed by employing a perturbative expansion in the
ratio rho/V between the matter energy density on the branes and the brane
tensions around the static Randall-Sundrum solution (which has rho=0 and brane
tensions +-V). This approach ensures that the matter evolves adiabatically and
allows us to find approximate solutions to second order in \rho/V. Some
particular cases are then analyzed in details.Comment: 17 pages, RevTeX4, 4 figures, final version to appear in Phys. Rev.
Interdependence between integrable cosmological models with minimal and non-minimal coupling
We consider the relation between exact solutions of cosmological models
having minimally and non-minimally coupled scalar fields. This is done for a
particular class of solvable models which, in the Einstein frame, have
potentials depending on hyperbolic functions and in the Jordan frame, where the
non-minimal coupling is conformal, possess a relatively simple dynamics. We
show that a particular model in this class can be generalized to the cases of
closed and open Friedmann universes and still exhibits a simple dynamics.
Further we illustrate the conditions for the existences of bounces in some
sub-classes of the set of integrable models we have considered.Comment: 15 pages, v2: figures and references added, accepted for publication
in CQ
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