2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/82584We address the question of the microscopic origin of dissipation in collective motion of a quantum many--body system in the framework of a parametric random matrix approach to the intrinsic dynamics. We show that the fluctuation--dissipation theorem is generally violated and, moreover, energy diffusion has a markedly non--Gaussian character and the corresponding distribution has very long tails. Such features do not support a Langevin or Fokker--Planck approach to dissipation in collective nuclear motion.11 pages (Latex), 3 figures (uuencoded postscript)Nuclear Theorytext