Causal Propagation of a Charged Spin 3/2 Field in an External Electromagnetic Background
arXiv:0906.1432 · doi:10.1103/PhysRevD.80.025009
Abstract
We present a Lagrangian for a massive, charged spin 3/2 field in a constant external electromagnetic background, which correctly propagates only physical degrees of freedom inside the light cone. The Velo-Zwanziger acausality and other pathologies such as loss of hyperbolicity or the appearance of unphysical degrees of freedom are avoided by a judicious choice of non-minimal couplings. No additional fields or equations besides the spin 3/2 ones are needed to solve the problem.
10 pages, references added. To appear in PRD