Combining cosmological and local bounds on bimetric theory

TL;DR

This paper tests ghost-free bimetric theory against cosmological and local gravity observations, constraining its parameters and identifying models consistent with current data.

Contribution

It provides the first comprehensive confrontation of bimetric theory with both cosmological and local gravity tests using a new physical parametrisation.

Findings

All models considered are compatible with cosmological data.

Most models are consistent with local gravity tests.

The minimal bimetric model with only β₁ is ruled out.

Abstract

Ghost-free bimetric theory describes two nonlinearly interacting spin-2 fields, one massive and one massless, thus extending general relativity. We confront bimetric theory with observations of Supernovae type 1a, Baryon Acoustic Oscillations and the Cosmic Microwave Background in a statistical analysis, utilising the recently proposed physical parametrisation. This directly constrains the physical parameters of the theory, such as the mass of the spin-2 field and its coupling to matter. We find that all models under consideration are in agreement with the data. Next, we compare these results to bounds from local tests of gravity. Our analysis reveals that all two- and three-parameter models are observationally consistent with both cosmological and local tests of gravity. The minimal bimetric model (only $\beta_1$) is ruled out by our combined analysis.