Exact solution of a Levy walk model for anomalous heat transport

TL;DR

This paper provides an exact analytical solution for a Levy walk model describing anomalous heat transport in one-dimensional systems, revealing non-local current-temperature relations and fluctuation properties.

Contribution

It offers the first exact calculations of heat current, fluctuation large deviation function, and temperature profile for Levy walk models in steady state.

Findings

Heat current is non-locally related to temperature gradient.

All current fluctuation cumulants share the same size dependence.

A size-dependent cutoff time is needed for ring geometries to mimic mechanical models.

Abstract

The Levy walk model is studied in the context of the anomalous heat conduction of one dimensional systems. In this model the heat carriers execute Levy-walks instead of normal diffusion as expected in systems where Fourier's law holds. Here we calculate exactly the average heat current, the large deviation function of its fluctuations and the temperature profile of the Levy-walk model maintained in a steady state by contact with two heat baths (the open geometry). We find that the current is non-locally connected to the temperature gradient. As observed in recent simulations of mechanical models, all the cumulants of the current fluctuations have the same system-size dependence in the open geometry. For the ring geometry, we argue that a size dependent cut-off time is necessary for the Levy walk model to behave as mechanical models. This modification does not affect the results on transport in the open geometry for large enough system sizes.