Dynamics of expansion of the Universe in the models with non-minimally coupled dark energy

TL;DR

This paper investigates how different types of interactions between dark energy and dark matter affect the universe's expansion, deriving conditions for positive densities and analyzing the resulting dynamics.

Contribution

It introduces a model with three interaction types between dark energy and dark matter, analyzing their effects on cosmological expansion and density positivity.

Findings

Existence of parameter ranges with negative densities

Conditions for positive dark energy and dark matter densities

Constraints on interaction parameters for physical viability

Abstract

We consider the dark energy model with barotropic equation of state, which interacts with dark matter through gravitation and another force, causing the energy-momentum exchange between them. Both components are described in approximation of ideal fluids, which are parametrized by density and equation of state parameters. Three types of interactions between dark components are considered: the interaction independent from their densities, the one proportional to density of dark energy and the one proportional to density of dark matter. The equations which describe the expansion dynamics of homogeneous and isotropic Universe and evolution of densities of both components for different values of interaction parameter are obtained on the bases of the general covariant conservation equations and Einstein's ones. For three kinds of interactions we show the existence of the range of values of parameters of dark energy for which the densities of dark components and their sum are negative. We find the conditions of positivity of density of dark energy and dark matter. The constraints on the value of parameter of interaction are derived. The dynamics of expansion of the Universe with these interactions of dark energy and dark matter is analysed.