Doubly coupled matter fields in massive bigravity

TL;DR

This paper investigates non-minimal matter couplings in massive bigravity, analyzing their cosmological implications and providing a comprehensive perturbation analysis beyond previous special solutions.

Contribution

It offers a complete perturbation analysis for general backgrounds in bimetric gravity with non-minimal matter couplings, extending prior work on special solution branches.

Findings

Couplings are ghost-free below the strong coupling scale.

Enrichment of phenomenology in massive gravity models.

Complete perturbation analysis for general backgrounds.

Abstract

In the context of massive (bi-)gravity non-minimal matter couplings have been proposed. These couplings are special in the sense that they are free of the Boulware-Deser ghost below the strong coupling scale and can be used consistently as an effective field theory. Furthermore, they enrich the phenomenology of massive gravity. We consider these couplings in the framework of bimetric gravity and study the cosmological implications for background and linear tensor, vector, and scalar perturbations. Previous works have investigated special branch of solutions. Here we perform a complete perturbation analysis for the general background equations of motion completing previous analysis.