Cosmology of F(R) nonlinear massive gravity
  The theory of nonlinear massive gravity can be extended into the F(R) form as
developed in Phys.Rev.D90, 064051 (2014). Being free of the Boulware-Deser
ghost, such a construction has the additional advantage of exhibiting no linear
instabilities around a cosmological background. We investigate various
cosmological evolutions of a universe governed by this generalized massive
gravitational theory. Specifically, under the Starobinsky ansantz, this model
provides a unified description of the cosmological history, from early-time
inflation to late-time self-acceleration. Moreover, under viable F(R) forms,
the scenario leads to a very interesting dark-energy phenomenology, including
the realization of the quintom scenario without any pathology. Finally, we
provide a detailed analysis of the cosmological perturbations at linear order,
as well as the Hamiltonian constraint analysis, in order to examine the
physical degrees of freedom.
