Revisiting perturbations in extended quasidilaton massive gravity
  In this work we study the theory of extended quasidilaton massive gravity
together with the presence of matter fields. After discussing the homogeneous
and isotropic fully dynamical background equations, which governs the exact
expansion history of the universe, we consider small cosmological perturbations
around these general FLRW solutions. The stability of tensor, vector and scalar
perturbations on top of these general background solutions give rise to
slightly different constraints on the parameters of the theory than those
obtained in the approximative assumption of the late-time asymptotic form of
the expansion history, which does not correspond to our current epoch. This
opens up the possibility of stable FLRW solutions to be compared with current
data on cosmic expansion with the restricted parameter space based on
theoretical ground.
