Evolution of cosmological perturbations in the models with interacting dynamical dark energy

TL;DR

This paper investigates how cosmological perturbations evolve in models where dark energy interacts non-gravitationally with dark matter, considering a time-varying equation of state and analyzing stability and perturbation dynamics.

Contribution

It introduces a model with interacting dynamical dark energy characterized by a variable EoS and derives stability conditions, extending previous models with constant EoS.

Findings

Interaction affects density and velocity perturbations.

Stability conditions depend on interaction strength.

Model avoids non-adiabatic instabilities during radiation epoch.

Abstract

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 model with constant EoS, because it avoids non-adiabatic instabilities of dark energy at radiation dominated epoch for certain types of interaction in dark sector. The stability conditions for solutions of equations of dark energy perturbations were derived. The impact of strength of additional interaction between dark components on the evolution of density and velocity perturbations in them is analysed for quintessence and phantom types of dark energy.