Wave four-tensor of a plane light wave in free space with application to the positive mass theorem in general relativity

Abstract

The positive mass theorem in general relativity states that in an asymptotically flat spacetime, if the momentum–energy tensor is divergence-free and satisfies a dominant energy condition, then a total momentum–energy four-vector can be formed, of which the energy component is nonnegative. In this paper, we take the wave four-tensor of a plane light wave in free space as a counterexample to show that there is no guarantee that a total four-vector can be formed. Thus the theoretical framework for the positive mass theorem is flawed. In addition, it is also shown as well that the Lorentz covariance of Dirac wave equation is not compatible with Einstein mass–energy equivalence.