Two-Field Quintom Models in the w-w' Plane

The w-w' plane, defined by the equation of state parameter for the dark energy and its derivative with respect to the logarithm of the scale factor, is useful to the study of classifying the dynamical dark energy models. In this note, we examine the evolving behavior of the two-field quintom models with w crossing the w=-1 barrier in the w-w' plane. We find that these models can be divided into two categories, type A quintom in which w changes from >-1 to <-1 and type B quintom in which w changes from -1 as the universe expands.Comment: 5 pages, 2 figures, RevTeX, Accepted for publication as a Brief Report in Physical Review

Cosmological Evolution of a Quintom Model of Dark Energy

We investigate in this paper the cosmological evolution of a dark energy model with two scalar fields where one of the scalar has canonical kinetic energy and another scalar has negative kinetic energy term. For such a system with exponential potentials we find that during the evolution of the universe the equation of state $w$ changes from $w>-1$ to $w<-1$, which is consistent with the recent observations. A phase-plane analysis shows that the "phantom"-dominated scaling solution is the stable late-time attractor of this type of models.Comment: 9 pages, 3 figures, LaTeX2