2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/82816Based on the formalism of thermo-field dynamics a new approach for studying collective excitations in hot finite Fermi systems is presented. Two approximations going beyond the thermal RPA namely renormalized thermal RPA and thermal second RPA are formulated.8 pages, no figuresNuclear Theorytext