2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54603We provide an axiomatic framework for Quantum Field Theory at finite temperature which implies the existence of general analyticity properties of the $ n $-point functions; the latter parallel the properties derived from the usual Wightman axioms in the vacuum representation of Quantum Field Theory. Complete results are given for the propagators, including a generalization of the Källén-Lehmann representation. Some known examples of ``hard-thermal-loop calculations'' and the representation of ``quasiparticles'' are discussed in this general framework.23 pages, TEX, no figures, to appear in Ann. Inst. H. PoincareHigh Energy Physics - TheoryHigh Energy Physics - Phenomenologytext