Decoupling Solution Moduli of Bigravity

TL;DR

This paper classifies exact solutions in ghost-free bigravity, showing how background and foreground metrics can decouple, leading to a scenario where both metrics behave as general relativity with an effective cosmological constant.

Contribution

It provides a complete classification of solutions allowing decoupling of metrics in ghost-free bigravity, revealing conditions under which both metrics follow GR dynamics.

Findings

Decoupling solutions enable background and foreground metrics to behave as GR with a cosmological constant.

The solution space includes cases where the two metrics evolve independently as GR.

The classification facilitates understanding of the solution landscape in ghost-free bigravity.

Abstract

A complete classification of exact solutions of ghost-free, massive bigravity is derived which enables the dynamical decoupling of the background, and the foreground metrics. The general decoupling solution space of the two metrics is constructed. Within this branch of the solution space the foreground metric theory becomes general relativity (GR) with an additional effective cosmological constant, and the background metric dynamics is governed by plain GR.