Self-accelerating Massive Gravity: Exact solutions for any isotropic
  matter distribution
  We present an exact solution to the equations of massive gravity that
displays cosmological constant-like behavior for any spherically symmetric
distribution of matter, including arbitrary time dependence. On this solution,
the new degrees of freedom from the massive graviton generate a cosmological
constant-like contribution to stress-energy that does not interact directly
with other matter sources. When the effective cosmological constant
contribution dominates over other sources of stress energy the cosmological
expansion self-accelerates, even when no other dark-energy-like ingredients are
present. The new degrees of freedom introduced by giving the graviton the mass
do not respond to arbitrarily large radial or homogeneous perturbations from
other matter fields on this solution. We comment on possible implications of
this result.
