Cosmological constraints on ghost-free bigravity: background dynamics and late-time acceleration

TL;DR

This paper investigates a ghost-free bigravity model's ability to explain late-time cosmic acceleration without dark energy, by analyzing its background cosmology and fitting it to observational data.

Contribution

It provides a comprehensive analysis of the background cosmology of ghost-free bigravity and assesses its viability as an alternative to dark energy through statistical constraints.

Findings

Model fits cosmological data well

Can explain acceleration without dark energy

Certain caveats in interpretation

Abstract

The recent discovery of a ghost-free, non-linear extension of the Fierz-Pauli theory of massive gravity, and its bigravity formulation, introduced new possibilities of interpreting cosmological observations, in particular, the apparent late-time accelerated expansion of the Universe. Here we discuss such possibilities by studying the background cosmology of the model and comparing its predictions to different cosmological measurements. We place constraints on the model parameters through an extensive statistical analysis of the model, and compare its viability to that of the standard model of cosmology. We demonstrate that the model can yield perfect fits to the data and is capable of explaining the cosmic acceleration in the absence of an explicit cosmological constant or dark energy, but there are a few caveats that must be taken into account when interpreting the results.