9 research outputs found
Emergent universe in a Jordan-Brans-Dicke theory
In this paper we study emergent universe model in the context of a self
interacting Jordan-Brans-Dicke theory. The model presents a stable past eternal
static solution which eventually enters a phase where the stability of this
solution is broken leading to an inflationary period. We also establish
constraints for the different parameters appearing in our model.Comment: 18 pages, 4 figures. Accepted for publication in JCA
Tachyonic Universes in Patch Cosmologies with
In this article we study closed inflationary universe models by means of a
tachyonic field. We described a general treatment for created a universe with
in patch cosmology, which is able to represent General Relativity,
Gauss-Bonnet or Randall-Sundrum patches. We use recent data from astronomical
observations to constrain the parameters appearing in our model.Comment: 15 pages, 2 figures. Accepted by Modern Physics Letters
On the Stability of Jordan-Brans-Dicke Static Universe
In this work we study the stability of the Jordan-Brans-Dicke (JBD) static
universe. This is motivated by the possibility that the universe might have
started out in an asymptotically JBD static state, in the context of the so
called emergent universe scenario. We extent our previous results on stability
of JBD static universe by considering spatially homogeneous Bianchi type IX
anisotropic perturbation modes and by including more general perfect fluids.
Contrary to general relativity, we have found that the JBD static universe,
dominated by a standard perfect fluid, could be stable against isotropic and
anisotropic perturbations. The implications of these results for the initial
state of the universe and its pre-inflationary evolution are discussed.Comment: 24 pages, 2 figures, typos corrected, some improvements in section 4
and comments added in conclusions. References added. Accepted for publication
in JCA