Kubo formulas for dispersion in heterogeneous periodic non-equilibrium systems

TL;DR

This paper derives a general Kubo-like formula for effective diffusion and drift in non-equilibrium heterogeneous periodic media, enabling straightforward computation of dispersion properties in complex systems.

Contribution

It introduces a universal formula for the effective diffusion tensor in non-equilibrium periodic media, including explicit finite-time corrections and analytical solutions in one dimension.

Findings

Derived a Kubo-like formula for effective diffusion tensor.

Provided explicit formulas for late-time transport coefficients.

Established a method for computing dispersion in arbitrary non-equilibrium systems.

Abstract

We consider the dispersion properties of tracer particles moving in non-equilibrium heterogeneous periodic media. The tracer motion is described by a Fokker-Planck equation with arbitrary spatially periodic (but constant in time) local diffusion tensors and drift, eventually with the presence of obstacles. We derive a Kubo-like formula for the time dependent effective diffusion tensor valid in any dimension. From this general formula, we derive expressions for the late time effective diffusion tensor and drift in these systems. In addition, we find an explicit formula for the late finite time corrections to these transport coefficients. In one dimension, we give closed analytical formula for the transport coefficients. The formulas derived here are very general and provide a straightforward method to compute the dispersion properties in arbitrary non-equilibrium periodic advection-diffusion systems.