2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/126549A common assumption in quantum field theory is that the energy-momentum 4-vector of any quantum state must be time-like. However it has been recently shown [4] that this is not the case for a Dirac-Maxwell field in the coulomb gauge. Here we will present a proof that is simpler then the proof of Ref. [4] that there must exist quantum states which are space-like for a Dirac-Maxwell field in the coulomb gauge.9 pagesQuantum Physicstext