Eigenstate Thermalization Hypothesis and Free Probability
Abstract
Quantum thermalization is well understood via the Eigenstate Thermalization Hypothesis (ETH). The general form of ETH, describing all the relevant correlations of matrix elements, may be derived on the basis of a `typicality' argument of invariance with respect to local rotations involving nearby energy levels. In this work, we uncover the close relation between this perspective on ETH and Free Probability theory, as applied to a thermal ensemble or an energy shell. This mathematical framework allows one to reduce in a straightforward way higher-order correlation functions to a decomposition given by minimal blocks, identified as free cumulants, for which we give an explicit formula. This perspective naturally incorporates the consistency property that local functions of ETH operators also satisfy ETH. The present results uncover a direct connection between the Eigenstate Thermalization Hypothesis and the structure of Free Probability, widening considerably the latter's scope and highlighting its relevance to quantum thermalization.
Cite
@article{arxiv.2204.11679,
title = {Eigenstate Thermalization Hypothesis and Free Probability},
author = {Silvia Pappalardi and Laura Foini and Jorge Kurchan},
journal= {arXiv preprint arXiv:2204.11679},
year = {2023}
}
Comments
5 pages, 2 figures and 5 pages of supplementary material. This paper has been submitted simultaneously with "Dynamics of Fluctuations in the Open Quantum SSEP and Free Probability" by L. Hruza and D. Bernard, which discusses the appearance of free cumulants in stochastic a transport model