2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/207767An often used rule that the thermal correction to the self-energy is the thermal phase-space times the forward scattering amplitude from target particles is shown to be the leading term in an exact multiple scattering expansion. Starting from imaginary-time finite-temperature field theory, a rigorous expansion for the retarded self-energy is derived. The relationship to the thermodynamic potential is briefly discussed.33 pages. Uses ReVTeX and epsf. 8 figuresHigh Energy Physics - PhenomenologyNuclear Theorytext