Seminarium Teorii Względności i Grawitacji

I will discuss linear perturbations of the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model in the Regge-Wheeler formalism which is a standard framework to study perturbationsof spherically-symmetric black holes. In particular, I will show that the general solution of linear perturbation equations can be given in terms of two copies of a master scalar satisfying scalar wave equation on the FLRW background (with a Regge-Wheeler/Zerilli type potential) thus representing two gravitational degrees of freedom, and one scalar satisfying a transport type equation representing matter perturbation. It is expected that the Regge-Wheeler formalism can be easily extended to includenonlinear perturbations, akin to the recent work [Phys. Rev. D 96, 124026 (2017)].