Notes on diffeomorphisms symmetry of f(R) gravity in the cosmological

چکیده مقاله

We study the metric perturbations in the context of restricted f(R) gravity, in which a parameter for deviation the full diffeomorphisms of space-time is introduced. We demonstrate that one can choose the parameter to remove the induced anisotropic stress, which is present in the usual f(R) gravity. Moreover, to prevent instability for the vector and tensor metric perturbations, some constraints on the model are obtained.