Dynamics of interacting dark energy

TL;DR

This paper explores models where dark energy and dark matter interact through energy exchange, providing new solutions and conditions to ensure physical viability, thereby advancing understanding of the dark sector's dynamics.

Contribution

It introduces a new exact solution for a previously studied class and general conditions for both classes to prevent unphysical behaviors.

Findings

New exact solution for the first class of models

General conditions to avoid negative energy densities

Extended analysis of the second class of models

Abstract

Dark energy and dark matter are only indirectly measured via their gravitational effects. It is possible that there is an exchange of energy within the dark sector, and this offers an interesting alternative approach to the coincidence problem. We consider two broad classes of interacting models where the energy exchange is a linear combination of the dark sector densities. The first class has been previously investigated, but we define new variables and find a new exact solution, which allows for a more direct, transparent and comprehensive analysis. The second class has not been investigated in general form before. We give general conditions on the parameters in both classes to avoid unphysical behavior (such as negative energy densities).