EVOLUTION OF COSMOLOGICAL PERTURBATIONS IN THE MODELS WITH INTERACTING DYNAMICAL DARK ENERGY

Evolution of cosmological perturbations is considered in the model with dynamical dark energy which non-gravitationally interacts with dark matter. The dark energy equation of state parameter (EoS) is varying in time and is parameterized by its adiabatic sound speed. Such model of interacting dark energy has advantages over the model with constant EoS, because it avoids non-adiabatic instabilities of dark energy in the radiation dominated epoch for certain types of interaction in the dark sector. The stability conditions for the solutions of equations of dark energy perturbations were derived. The impact of the strength of additional interaction between dark components on the evolution of the density and velocity perturbations in them is analysed for the quintessence and phantom types of dark energy.