Lorentz covariant and gauge invariant description of orbital and spin angular momentum and the non-symmetric energy momentum tensor

Abstract: Starting from covariant expressions, a gauge independent separation of orbital and spin angular momentum for electrodynamics is presented. This results from the non-symmetric canonical energy momentum tensor of the electromagnetic field. The origin of the difficulty is discussed and a covariant gauge invariant spin vector is derived. The paradox concerning the spin angular momentum of a plane wave finds a natural solution.