A comment on the averaging in an inhomogeneous cosmology and the Hubble constant problem

Abstract

Abstract In recent cosmology, the Hubble constant problem has attracted much attention. As a possible solution to the problem, local variation of the expansion rate in an inhomogeneous cosmology has been proposed, where the spatial averaging over a finite domain was introduced in order to construct local Friedmann spacetime. However, the treatment was restricted to the comoving synchronous gauge and there is some confusion over the gauge ambiguity of the results. In this paper we study the spatial averaging in the Newtonian gauge in order to clarify the gauge ambiguity and obtain the same results as before.