On Energy and Momentum of the Friedman and Some More General Universes

TL;DR

This paper challenges previous coordinate-dependent conclusions by demonstrating that energy and momentum in Friedman and similar universes are not necessarily zero, using coordinate-independent methods.

Contribution

It introduces coordinate-independent expressions for energy and momentum, showing these universes can have non-zero energy and momentum.

Findings

Previous zero energy conclusions are coordinate-dependent.

Coordinate-independent methods reveal non-zero energy and momentum.

Friedman universes are not necessarily energetically null.

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}. By using new coordinate independent expressions on energy and momentum one can show that the Friedman and more general universes {\it needn't be energetic nonentity}.