Cosmological Solutions in Bimetric Gravity and their Observational Tests

TL;DR

This paper derives cosmological evolution equations in bimetric gravity, showing they can replicate the universe's expansion history and fit observational data, offering a viable alternative to standard cosmology.

Contribution

It provides the first comprehensive analytic solutions for bimetric gravity cosmology and demonstrates their consistency with observational data.

Findings

Models can reproduce the cosmic expansion history.

Solutions relax to de Sitter or anti-de Sitter phases.

Fits observational data from supernovae, CMB, BAO.

Abstract

We obtain the general cosmological evolution equations for a classically consistent theory of bimetric gravity. Their analytic solutions are demonstrated to generically allow for a cosmic evolution starting out from a matter dominated FLRW universe while relaxing towards a de Sitter (anti-de Sitter) phase at late cosmic time. In particular, we examine a subclass of models which contain solutions that are able to reproduce the expansion history of the cosmic concordance model inspite of the nonlinear couplings of the two metrics. This is demonstrated explicitly by fitting these models to observational data from Type Ia supernovae, Cosmic Microwave Background and Baryon Acoustic Oscillations.