2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45790It is shown that there is the possibility to find at least in the perturbation framework the Matsubara theory from the $S-$matrix interpretation of the real-time finite-temperature theory if the system under consideration is in an equilibrium state.8, LaTex, no figuresHigh Energy Physics - PhenomenologyComments to the $S$-matrix interpretation of finite-temperature field theoriestext