Anomalous energy transport in FPU-$\beta$ chain

TL;DR

This paper rigorously derives a fractional diffusion equation for heat transport in the FPU-$\beta$ chain, revealing anomalous energy transport behavior in a one-dimensional anharmonic crystal model.

Contribution

It provides the first rigorous derivation of an anomalous diffusion equation from the Boltzmann Phonon Equation for the FPU-$\beta$ chain.

Findings

Derivation of a fractional diffusion equation for heat transport.

Identification of anomalous diffusion behavior in the FPU-$\beta$ chain.

Connection between microscopic phonon dynamics and macroscopic heat transport.

Abstract

This paper is devoted to the derivation of a macroscopic fractional diffusion equation describing heat transport in an anharmonic chain. More precisely, we study here the so-called FPU-$\beta$ chain, which is a very simple model for a one-dimensional crystal in which atoms are coupled to their nearest neighbors by a harmonic potential, weakly perturbed by a quartic potential. The starting point of our mathematical analysis is a kinetic equation: Lattice vibrations, responsible for heat transport, are modeled by an interacting gas of phonons whose evolution is described by the Boltzmann Phonon Equation. Our main result is the rigorous derivation of an anomalous diffusion equation starting from the linearized Boltzmann Phonon Equation