Cosmological perturbations of massive gravity coupled to DBI Galileons
  Certain scalar fields with higher derivative interactions and novel classical
and quantum mechanical properties - the Galileons - can be naturally
covariantized by coupling to nonlinear massive gravity in such a way that their
symmetries and number of degrees of freedom are unchanged. We study the
propagating degrees of freedom in these models around cosmologically
interesting backgrounds. We identify the conditions necessary for such a theory
to remain ghost free, and consider when tachyonic instabilities can be avoided.
We show that on the self-accelerating branch of solutions, the kinetic terms
for the vector and scalar modes of the massive graviton vanish, as in the case
of pure massive gravity.
