Distribution of Time-Averaged Observables for Weak Ergodicity Breaking

TL;DR

This paper derives a general formula for the distribution of time-averaged observables in systems exhibiting weak ergodicity breaking, highlighting differences between normal and anomalous diffusion behaviors.

Contribution

It introduces a unified framework for understanding the distribution of time-averaged observables in subdiffusive systems, extending classical ergodic theory to weakly non-ergodic regimes.

Findings

Distribution of time-averaged position shows large fluctuations in subdiffusive systems

Recovers ergodic behavior and Boltzmann statistics for Gaussian random walks

Demonstrates non-ergodic behavior using Lévý's generalized central limit theorem

Abstract

We find a general formula for the distribution of time-averaged observables for systems modeled according to the sub-diffusive continuous time random walk. For Gaussian random walks coupled to a thermal bath we recover ergodicity and Boltzmann's statistics, while for the anomalous subdiffusive case a weakly non-ergodic statistical mechanical framework is constructed, which is based on L\'evy's generalized central limit theorem. As an example we calculate the distribution of $\bar{X}$: the time average of the position of the particle, for unbiased and uniformly biased particles, and show that $\bar{X}$ exhibits large fluctuations compared with the ensemble average $<X>$.