3 research outputs found
Crossing the Phantom Divide Line in a DGP-Inspired -Gravity
We study possible crossing of the phantom divide line in a DGP-inspired
braneworld scenario where scalar field and curvature quintessence
are treated in a unified framework. With some specific form of and
by adopting a suitable ansatz, we show that there are appropriate regions of
the parameters space which account for late-time acceleration and admit
crossing of the phantom divide line.Comment: 23 Pages, 10 figs, Submitted to JCA
Dilatonic ghost condensate as dark energy
We explore a dark energy model with a ghost scalar field in the context of
the runaway dilaton scenario in low-energy effective string theory. We address
the problem of vacuum stability by implementing higher-order derivative terms
and show that a cosmologically viable model of ``phantomized'' dark energy can
be constructed without violating the stability of quantum fluctuations. We also
analytically derive the condition under which cosmological scaling solutions
exist starting from a general Lagrangian including the phantom type scalar
field. We apply this method to the case where the dilaton is coupled to
non-relativistic dark matter and find that the system tends to become quantum
mechanically unstable when a constant coupling is always present. Nevertheless,
it is possible to obtain a viable cosmological solution in which the energy
density of the dilaton eventually approaches the present value of dark energy
provided that the coupling rapidly grows during the transition to the scalar
field dominated era.Comment: 26 pages, 6 figure
Gauss-Bonnet Cosmology with Induced Gravity and Non-Minimally Coupled Scalar Field on the Brane
We construct a cosmological model with non-minimally coupled scalar field on
the brane, where Gauss-Bonnet and Induced Gravity effects are taken into
account. This model has 5D character at both high and low energy limits but
reduces to 4D gravity in intermediate scales. While induced gravity is a
manifestation of the IR limit of the model, Gauss-Bonnet term and non-minimal
coupling of scalar field and induced gravity are essentially related to UV
limit of the scenario. We study cosmological implications of this scenario
focusing on the late-time behavior of the solutions. In this setup, non-minimal
coupling plays the role of an additional fine-tuning parameter that controls
the initial density of predicted finite density big bang. Also, non-minimal
coupling has important implication on the bouncing nature of the solutions.Comment: 33 pages, 12 figures, one table, revised and final version accepted
for publication in JCA