Gravitational ringdown in the minimal theory of massive gravity

This work focuses on gravitational perturbations of black holes in the self-accelerating branch of the minimal theory of massive gravity (MTMG). This theory is a healthy extension of general relativity (GR) which displays the feature of massive tensor modes, without additional polarizations, strong-coupling issues nor requiring screening mechanisms. We proceed by implementing a newly developed technique that, instead of considering a second-order Schr"odinger-like reformulation of perturbation equations, relies on a first-order formulation and solves it asymptotically, before numerically deriving the quasinormal modes. We find that the black holes of MTMG are stable, and that their quasinormal modes smoothly differ from the GR ones, for nonvanishing values of the graviton mass. This work hence confirms the fact that GR is a smooth limit of MTMG, and opens the exciting possibility of a clean test, performed for instance by the LISA detector.