Cosmology in massive gravity with effective composite metric

TL;DR

This paper investigates cosmological solutions in massive gravity with an effective composite metric, analyzing stability and perturbations, and finds stable de Sitter attractors relevant for late-time cosmic acceleration.

Contribution

It introduces a novel coupling of dark sector matter to an effective composite metric and studies the resulting cosmological dynamics and stability conditions.

Findings

Presence of stable de Sitter attractor points

Conditions for absence of ghost and gradient instabilities

Potential to distinguish from standard cosmology observationally

Abstract

This paper is dedicated to scrutinizing the cosmology in massive gravity. A matter field of the dark sector is coupled to an effective composite metric while a standard matter field couples to the dynamical metric in the usual way. For this purpose, we study the dynamical system of cosmological solutions by using phase analysis, which provides an overview of the class of cosmological solutions in this setup. This also permits us to study the critical points of the cosmological equations together with their stability. We show the presence of stable attractor de Sitter critical points relevant to the late-time cosmic acceleration. Furthermore, we study the tensor, vector and scalar perturbations in the presence of standard matter fields and obtain the conditions for the absence of ghost and gradient instabilities. Hence, massive gravity in the presence of the effective composite metric can accommodate interesting dark energy phenomenology, that can be observationally distinguished from the standard model according to the expansion history and cosmic growth.