Relaxation of the Cosmological Principle and the Friedman Robertson-Walker Cosmology

Abstract

The Cosmological Principle defines the Friedmann — Robertson — Walker (FRW) cosmological model in two steps. The first step concerns the definition of the FRW metric and the second the symmetry properties of the physical fields. The definition of the metric is achieved by means of symmetry assumptions basedon KVs, which are very strong and restrictive symmetries. We prove that one can define the FRW metric element using conformal Killing vectors, thus relaxing the demands of the Cosmological Principle on the symmetries of the mater fields. In addition we show how this approach leads to the consideration of a new set of conserved currents in the FRW spacetime.y