Selfacceleration with Quasidilaton
  Quasidilaton massive gravity is an extension of massive General Relativity to
a theory with additional scale invariance and approximate internal Galilean
symmetry. The theory has a novel self-accelerated solution with the metric
indistinguishable (in the decoupling limit) from the de Sitter space, its
curvature set by the graviton mass. The spectra of tensor, vector, and scalar
perturbations on this solution contain neither ghosts, nor gradient
instabilities or superluminal modes, for a range of the parameter space. This
represents an example of a self-accelerated solution with viable perturbations,
attainable within a low energy effective field theory.
