On the viability of bigravity cosmology
  We revisit the question of viability of bigravity cosmology as a candidate
for dark energy. In the context of the low energy limit model, where matter
couples to a single metric, we study linear perturbations around homogeneous
and isotropic backgrounds to derive the Poisson's equation for the Newtonian
potential. Extending to second order perturbations, we identify the Vainshtein
radius below which non-linear scalar self interactions conspire to reproduce GR
on local scales. We combine all of these results to determine the parameter
space that allows a late time de-Sitter attractor compatible with observations
and a successful Vainsthein mechanism. We find that the requirement on having a
successful Vainsthein mechanism is not compatible with the existence of
cosmological solutions at early times.
