2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/149066Resonant decay of the inflaton produces highly non-equilibrium states dominated by interacting classical waves. We discuss several topics in the theory of formation and evolution of such states.latex, 19 pages including 3 postscript figures; invited talk at "Strong and Electroweak Matter '97", 21-25 May 1997, Eger, Hungary; to appear in the Proceedings; minor correctionsHigh Energy Physics - Phenomenologytext