2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/39298In this talk, I review recent developments in equilibrium thermal field theory. Screened perturbation theory and hard-thermal-loop perturbation theory are discussed. A self-consistent $Φ$-derivable approach is also briefly reviewed.7 pages, 4 Postscript figures, uses espcrc1.sty. Invited talk given at the 5th Workshop on QCD, Villefranche-sur-Mer, France 3-7 JanHigh Energy Physics - Phenomenologytext