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.
