Studies of thermal conductivity in Fermi-Pasta-Ulam like lattices

Stefano Lepri, Roberto Livi, Antonio Politi

Published 2004-10-21, updated 2004-12-16Version 2

The pioneering computer simulations of the energy relaxation mechanisms performed by Fermi, Pasta and Ulam can be considered as the first attempt of understanding energy relaxation and thus heat conduction in lattices of nonlinear oscillators. In this paper we describe the most recent achievements about the divergence of heat conductivity with the system size in 1d and 2d FPU-like lattices. The anomalous behavior is particularly evident at low energies, where it is enhanced by the quasi-harmonic character of the lattice dynamics. Remakably, anomalies persist also in the strongly chaotic region where long--time tails develop in the current autocorrelation function. A modal analysis of the 1d case is also presented in order to gain further insight about the role played by boundary conditions.