Cosmology in General Massive Gravity Theories

TL;DR

This paper explores the cosmological implications of general massive gravity theories, showing how they can naturally account for dark energy with deviations from -1 in the equation of state, while analyzing their perturbative stability.

Contribution

It provides a comprehensive analysis of cosmology in general massive gravity theories, including the relation between strong coupling scales and dark energy properties.

Findings

Dark energy can be explained with massive gravity but requires deviation of w_eff from -1.

Strong coupling issues are linked to the background and symmetry breaking.

Weakly coupled regimes are possible with current experimental constraints.

Abstract

We study the cosmology of general massive gravity theories with five propagating degrees of freedom. This large class of theories includes both the case with a residual Lorentz invariance as the cases with simpler rotational invariance. We find that the existence of a nontrivial homogeneous FRW background, in addition to selecting the lorentz-breaking case, implies in general that perturbations around strict Minkowski or dS space are strongly coupled. The result is that dark energy can be naturally accounted for in massive gravity but its equation of state w_eff has to deviate from -1. We find indeed a relation between the strong coupling scale of perturbations and the deviation of w_eff from -1. Taking into account current limits on w_eff and submillimiter tests of the Newton's law as a limit on the possible strong coupling regime, we find that it is still possible to have a weakly coupled theory in a quasi dS background. Future experimental improvements may be used to predict w_eff in a weakly coupled massive gravity theory