Scalar phantom energy as a cosmological dynamical system

Abstract

Phantom energy can be visualized as a scalar field with a (non-canonical) negative kinetic energy term. We use the dynamical system formalism to study the attractor behavior of a cosmological model containing a phantom scalar field $\phi$ endowed with an exponential potential of the form $V(\phi)=V_0 \exp(-\lambda \kappa \phi)$, and a perfect fluid with constant equation of state $\gamma$; the latter can be of the phantom type too. As in the canonical case, three characteristic solutions can be identified. The scaling solution exists but is either unstable or of no physical interest. Thus, there are only two stable critical points which are of physical interest, corresponding to the perfect fluid and scalar field dominated solutions, respectively. The most interesting case arises for $0> \gamma > -\lambda^2/3$, which allows the coexistence of the three solutions. The main features of each solution are discussed in turn.