Vainshtein mechanism in Generalised Massive Gravity

We present a non-linear analysis of perturbations around cosmological solutions in Generalised Massive gravity. This Lorentz invariant theory is an extension de Rham, Gabadadze, Tolley massive gravity that propagates 5 degrees freedom while allowing stable open FLRW cosmologies. For minimal model supports self-accelerating background, we study the dynamics perturbations. find equation for scalar graviton distinct from analogues Horndeski and DHOST theories. numerically solve to new type nonlinear solution mode, confirm presence Vainshtein screening mechanism. show PPN parameter approaches its GR value at solar system scales satisfies current bounds.