2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45386Low-temperature expansion of the effective Lagrangian of the QED$_{3+1}$ with a uniform magnetic field and a finite chemical potential is performed. Temperature corrections, as well as zero-temperature expression for the effective Lagrangian are presented as finite sums over partially filled Landau levels.9 pages, LaTeXHigh Energy Physics - PhenomenologyCondensed Mattertext