Massive gravity and the suppression of anisotropies and gravitational waves in a matter-dominated contracting universe

TL;DR

This paper explores a modified gravity model with a massive graviton that maintains only two degrees of freedom and avoids ghosts, enabling non-singular bouncing cosmologies and suppressing anisotropies and gravitational waves.

Contribution

It introduces a ghost-free massive gravity model that supports non-singular bounces and addresses key issues in matter bounce scenarios.

Findings

Supports non-singular bouncing solutions

Suppresses anisotropies during contraction

Reduces gravitational wave spectrum

Abstract

We consider a modified gravity model with a massive graviton, but which nevertheless only propagates two gravitational degrees of freedom and which is free of ghosts. We show that non-singular bouncing cosmological background solutions can be generated. In addition, the mass term for the graviton prevents anisotropies from blowing up in the contracting phase and also suppresses the spectrum of gravitational waves compared to that of the scalar cosmological perturbations. This addresses two of the main problems of the matter bounce scenario.