1205.5713 (Mikhail S. Volkov)

Exact self-accelerating cosmologies in the ghost-free bigravity and
massive gravity    [PDF]

Mikhail S. Volkov

We present the most general exact cosmological solution in the ghost-free bigravity in the homogeneous and isotropic sector. It exists for any values of the theory parameters and is described by two metrics which can be separately diagonalized in two different coordinate systems related to each other by a lightlike boost. The physical metric describes a universe that can be spatially flat, open, or closed, and which shows the late time acceleration due to the effective cosmological term mimicked by the graviton mass. The second metric is AdS, which becomes flat in the limit where the massless graviton decouples, in which case the solution fulfills the equations of the ghost-free massive gravity. Together with the other previously studied cases, this completes the list of all possible homogeneous and isotropic cosmologies in the ghost-free theories.

View original: http://arxiv.org/abs/1205.5713