Generalised matter couplings in massive bigravity

TL;DR

This paper introduces a new family of consistent matter couplings in massive bigravity, extending previous models and analyzing their theoretical properties and limits, with implications for multi-gravity theories.

Contribution

It identifies and explores a novel class of matter couplings in massive bigravity, including their limits and conditions for consistency, generalizing to multi-gravity frameworks.

Findings

Discovered a new family of consistent matter couplings.

Analyzed decoupling limits, ADM decompositions, and Higuchi bounds.

Discussed the uniqueness and conditions of matter couplings.

Abstract

We investigate matter couplings in massive bigravity. We find a new family of such consistent couplings, including and extending known consistent matter couplings, and we investigate their decoupling limits, ADM decompositions, Higuchi bounds and further aspects. We show that differences to previous known consistent couplings only arise beyond the $\Lambda_3$ decoupling limit and discuss the uniqueness of consistent matter couplings and how this is related to the so-called symmetric vielbein condition. Since we work in a vielbein formulation, these results easily generalise to multi-gravity.