Cosmology in rotation-invariant massive gravity with non-trivial fiducial metric

Understand

We investigate the cosmology of SO(3)-invariant massive gravity with 5 degrees of freedom.

• In contrast with previous studies, we allow for a non-trivial fiducial metric, which can be justified by invoking, for example, a dilaton-like global symmetry.
• We write the homogeneous and isotropic equations of motion in this more general setup and identify, in particular, de Sitter solutions.
• We then study the linear perturbations around the homogeneous cosmological solutions, by deriving the quadratic Lagrangian governing the dynamics of scalar, vector and tensor modes.