7 research outputs found
Asymptotic behavior of Cardassian cosmologies with exponential potentials
In this paper we analyze the asymptotic behavior of Cardassian cosmological
models filled with a perfect fluid and a scalar field with an exponential
potential. Cardassian cosmologies arise from modifications of the Friedmann
equation, and among the different proposals within that framework we will
choose those of the form with . We construct two
three dimensional dynamical systems arising from the evolution equations,
respectively adapted for studying the high and low energy limits. Using
standard dynamical systems techniques we find the fixed points and characterize
the solutions they represent. We pay especial attention to the properties
inherent to the modifications and compare with the (standard) unmodified
scenario. Among other interesting results, we find there are no late-time
tracking attractors.Comment: 9 pages, 8 figures, revtex
Quintom cosmologies admitting either tracking or phantom attractors
In this paper we investigate the evolution of a class of cosmologies fuelled
by quintom dark energy and dark matter. Quintom dark energy is a hybrid of
quintessence and phantom which involves the participation of two reals scalar
fields playing the roles of those two types of dark energy. In that framework
we examine from a dynamical systems perspective the possibility that those
fields are coupled among them by considering an exponential potential with an
interesting functional dependence similar but not identical to others studied
before. The model we consider represents a counterexample to the typical
behavior of quintom models with exponential potentials because it admits either
tracking attractors (), or phantom attractors ().Comment: revtex4, 7 pages, 6 figure