Attractor solutions in interacting dark energy models

Abstract

We investigate a cosmological model in which dark energy, represented by a quintessential scalar field, is coupled to a dark-matter perfect fluid in the spatially flat Friedmann–Robertson–Walker Universe. This allows an energy exchange in the dark sector which could happen both at early times before recombination era or at late times. We use the coupling function Q=γρdmφ̇ which is induced by conformal transforming scalar-tensor and f(R) gravity theories to Einstein frame. It is argued that there is a connection between this coupling function and Q∝ρdmH. A dynamical analysis is used to show that there are early- and late-time attracting solutions for which the system evolves for a wide range of initial conditions. These attractors generalize the scaling solutions which have been already found in the non-interacting case.