We discuss the self-accelerating universe solutions in the framework of the potentially ghost-free, nonlinear massive gravity theory recently proposed by de Rham–Gabadadze–Tolley. The theory allows general Friedmann–Robertson–Walker solutions with negative curvature. The contribution of the mass terms at the background level is an effective cosmological constant term depending on the parameters of the theory. We also discuss the cosmological perturbations in these backgrounds, as well as similar solutions of the extended versions of the theory; the actions of the scalar and vector degrees do not undergo a modification with respect to general relativity, while the two polarizations of gravity waves acquire a time-dependent effective mass term. This may lead to a modification of the stochastic gravitational wave spectrum.
Cosmological perturbations of self-accelerating universe in nonlinear massive gravity
