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

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.