2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/36569It is well known that there can be negative energy densities in quantum field theory. Most of the work done in this area has involved free non-interacting systems. In this paper we show how a quantum state with negative energy density can be formulated for a Dirac field interacting with an Electromagnetic field. It will be shown that, for this case, there exist quantum states whose average energy density over an arbitrary volume is a negative number with an arbitrarily large magnitude.12 pagesGeneral Relativity and Quantum Cosmologytext