Energy and momentum of the Friedmann and more general universes

Abstract

Recently some authors concluded that the energy and momentum of the Fiedman universes, flat and closed, are equal to zero locally and globally (flat universes) or only globally (closed universes). The similar conclusion was also done for more general only homogeneous universes (Kasner and Bianchi type I). Such conclusions originated from coordinate dependent calculations performed only in comoving Cartesian coordinates by using the so-called {\it energy-momentum complexes}. But it is known that the energy-momentum complexes can be reasonably use only in precisely defined asymptotically flat spacetimes (at null or at spatial infinity) to calculate global energy and momentum. In this paper we show, by using new coordinate independent expressions on energy and momentum that the Friedman and more general universes {\it needn't be energetic nonentity}.