Cosmic Expansion in Extended Quasidilaton Massive Gravity
  Quasidilaton massive gravity offers a physically well-defined gravitational
theory with non-zero graviton mass. We present the full set of dynamical
equations governing the expansion history of the universe, valid during
radiation domination, matter domination, and a late-time self-accelerating
epoch related to the graviton mass. The existence of self-consistent solutions
constrains the amplitude of the quasi-dilaton field and the graviton mass, as
well as other model parameters. We point out that the effective mass of
gravitational waves can be significantly larger than the graviton mass, opening
the possibility that a single theory can explain both the late-time
acceleration of the cosmic expansion and modifications of structure growth
leading to the suppression of large-angle correlations observed in the cosmic
microwave background.
