Interactions and Instabilities in Cosmology's Dark Sector

TL;DR

This paper examines how couplings between dark energy and dark matter can lead to instabilities, significantly constraining models of the dark sector in cosmology.

Contribution

It introduces the concept of adiabatic instability in interacting dark sector models, providing new constraints on their viability.

Findings

Adiabatic regime can cause catastrophic instability in dark sector models.

The instability imposes tight constraints on coupling strengths.

Certain interacting models are ruled out due to this instability.

Abstract

I consider couplings between the dark energy and dark matter sectors. I describe how the existence of an adiabatic regime, in which the dark energy field instantaneously tracks the minimum of its effective potential, opens the door for a catastrophic instability. This {\it adiabatic instability} tightly constrains a wide class of interacting dark sector models. This talk was presented at, and will appear in the proceedings of the DPF-2009 conference.