2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/170682We consider the energy current correlation function for the FPU-beta lattice. For small non-linearity one can rely on kinetic theory. The issue reduces then to a spectral analysis of the linearized collision operator. We prove thereby that, on the basis of kinetic theory, the energy current correlations decay in time as t^(-3/5). It follows that the thermal conductivity is anomalous, increasing as N^(2/5) with the system size N.33 pages, 2 EPS figuresMathematical Physics80A20; 74A25; 82C21; 46N55text