2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/53606The relativistic semi-classical approximation for a free massive particle is studied using the Wigner-Weyl formalism. A non-covariant Wigner function is proposed using the Newton-Wigner position operator. The perturbative solution for the time evolution is found. Causality is found to be perturbatively respected.6 pagesHigh Energy Physics - Theorytext