Dynamical analysis of the cosmology of mass-varying massive gravity

We study cosmological evolutions of the generalized model of nonlinear massive gravity in which the graviton mass is given by a rolling scalar field and is varying along time. By performing dynamical analysis, we derive the critical points of this system and study their stabilities. These critical points can be classified into two categories depending on whether they are identical with the traditional ones obtained in General Relativity. We discuss the cosmological implication of relevant critical points.