2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/221179The influence of a Zeeman magnetic field on the superconducting characteristics of the attractive Hubbard model was investigated. The ground state and temperature phase diagrams were obtained for a fixed number of particles. Two critical magnetic fields were found for the first order phase transition from the superconducting to the normal state for $n\neq 1$. For some range of parameters a reentrant transition was found and gapless superconductivity was obtained. The significance of the Hartree term was also analyzed.Minor changes. 5 pages, 2 figures, presented at The European Conference Physics of Magnetism 2008, June 24-27, Poznan, PolandStrongly Correlated ElectronsSuperconductivitytext