2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45773Dispersion relations for fermions at high temperature and in a background magnetic field are calculated in two different ways. First from a straightforward one-loop calculation where, in the weak field limit, we find an expression closely related to the standard dispersion relations in the absence of the magnetic field. Secondly, we derive the dispersion relations directly from the Hard Thermal Loop effective action, which allows for an exact solution (i.e. to all orders in the external field), up to the last numerical integrals.Latex+epsf with uuencoded ps-figuresHigh Energy Physics - PhenomenologyHigh Energy Physics - TheoryNuclear Theorytext