7 research outputs found

    Asymptotic behavior of Cardassian cosmologies with exponential potentials

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    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 3H2ρρn3H^2-\rho\propto \rho^n with n<1n<1. 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

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    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 (w=0w=0), or phantom attractors (w<1w<-1).Comment: revtex4, 7 pages, 6 figure
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