The diffusion equation for non-Markovian Gaussian stochastic processes
Statistical Mechanics
2026-05-19 v3
Abstract
We derive the exact evolution equation for the probability density function of particle displacements generated by arbitrary Gaussian velocity processes, when neither Markovianity and nor stationarity are assumed. Starting from the characteristic function of the density of the position, we construct a systematic hierarchy of equations based on Wick's theorem, in which the dynamics is governed by sums of geometrically connected Wick contractions. This approach yields a closed non-Markovian diffusion equation that generalizes the Fokker-Planck description and preserves Gaussianity only in the infinite-order limit.
Cite
@article{arxiv.2605.10561,
title = {The diffusion equation for non-Markovian Gaussian stochastic processes},
author = {Alessandro Taloni and Gianni Pagnini and Aleksei Chechkin},
journal= {arXiv preprint arXiv:2605.10561},
year = {2026}
}