Lorentz transformations of observable and ghost particle states in quantum electrodynamics and in a massive gauge theory

Abstract

Derivations are given of the effect of Lorentz boosts on physical particle and ghost states in quantum electrodynamics. It is shown that the photon helicity is an invariant even though, in general, Lorentz boosts transform the transverse, longitudinal, and timelike components of the vector potential into each other. A similar calculation is made for an Abelian gauge theory in which the particles have dynamical mass.