Generalized dark energy interactions with multiple fluids

TL;DR

This paper analyzes a scalar field model of dark energy coupled to multiple fluids, providing a comprehensive dynamical system analysis and exploring stability and observational constraints.

Contribution

It presents the most complete dynamical system analysis of a scalar field coupled to dust and radiation, including stability and observational constraints.

Findings

Stable fixed points identified for scalar field-fluid systems

Constraints on disformal coupling from Big-Bang Nucleosynthesis

Limits on variation of the fine-structure constant

Abstract

In the search for an explanation for the current acceleration of the Universe, scalar fields are the most simple and useful tools to build models of dark energy. This field, however, must in principle couple with the rest of the world and not necessarily in the same way to different particles or fluids. We provide the most complete dynamical system analysis to date, consisting of a canonical scalar field conformally and disformally coupled to both dust and radiation. We perform a detailed study of the existence and stability conditions of the systems and comment on constraints imposed on the disformal coupling from Big-Bang Nucleosynthesis and given current limits on the variation of the fine-structure constant.