2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56102A common assumption in quantum field theory is that the energy-momentum 4-vector of any quantum state must be timelike. It will be proven that this is not the case for a Dirac-Maxwell field. In this case quantum states can be shown to exist whose energy-momentum is spacelike. This implies that there must exist quantum states with less energy than the vacuum state.23 pages, minor errors correctedHigh Energy Physics - Theorytext