``Front'' Description in Relativistic Quantum Mechanics

Abstract

The problem of introducing a Cartesian position operator canonically conjugate to the momentum operator into relativistic one‐particle theories is investigated independent of any particular relativistic wave equation. The known result that such a description is possible for particles with nonvanishing mass is rederived. The general problem of introduction of canonical variables into relativistic theories is formulated and solved. The configurational indices so obtained correspond to directed plane wavefronts rather than point particles.