Dark matter-dark energy exchanges in an expanding universe

Abstract

We revisit Aydiner's 'Chaotic universe model' (2018) that considers a hypothetical coupling between dark matter and dark energy in a spatially flat, Friedman-Robertson-Walker universe. In this model, dark matter and dark energy are perfect fluids able to transform into each other through a specified coupling function. We extend Aydiner's analysis by dropping his assumption of a constant Hubble parameter, an assumption that is valid only on short time scales. In this more general setting, and using a dynamical systems approach, we explore the effect of coupling on the dark matter/energy densities. We show that the cyclic dynamics between the two dark elements persists only when w_dₑ > -1. For other values of w_dₑ, either dark matter vanishes and dark energy becomes constant or both disappear completely.