2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/47158In order to investigate the reliability of the classical approximation for non-perturbative real time correlation functions at finite temperature we study the two-point correlator for the anharmonic oscillator. For moderately large times the classical limit gives a good approximation of the quantum result but after some time $t_*$ the classical approximation breaks down even at high temperature.6 pages, Talk given at the E"otv"os Conference in Science: Strong and Electroweak Matter, Eger, Hungary, 21-25 May 1997High Energy Physics - Phenomenologytext