Universality classes of thermalization and energy diffusion.

Abstract

In this paper, we show that classical lattices can be classified into two universality classes for thermalization, based solely on the properties of their eigenmodes. This discovery is a consequence of our systematic multiwave quasiresonance analysis, a tool developed to this end. Lattices with extended modes belong to one class that can thermalize within a finite time, even when the nonlinearity strength is very weak, provided the system size is sufficiently large. In contrast, lattices with purely localized modes fall into another class. For these systems, the scaling behavior of thermalization time shifts stepwise from low-order to progressively higher-order quasiresonances as nonlinear strength decreases, implying that thermalization may become unattainable within a reasonable time for sufficiently weak nonlinearity strength. Furthermore, we show that the real-space energy diffusion behavior of the two classes is qualitatively different as well.