Thermalisation as Diffusion in Hilbert Space

Fuente: arXiv
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Autore principale: Lunkin, Aleksey
Natura: Preprint
Pubblicazione: 2026
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author Lunkin, Aleksey
author_facet Lunkin, Aleksey
contents We develop a microscopic theory of thermalisation for a thermometer coupled to a many-body bath beyond standard Markovian and Fermi-golden-rule assumptions. By modeling interaction matrix elements in the non-interacting basis as independent random variables, we derive a diffusion-propagator expression for the reduced dynamics and show that relaxation is controlled by the distribution of interaction-induced level broadenings. The theory predicts a thermalisation timescale set by the inverse typical broadening and yields a non-Markovian generalization of global balance. Exact-diagonalization tests for heavy-tailed L{é}vy couplings, an all-to-all transverse-field Ising model, and the one-dimensional Imbrie model show good agreement with these predictions.
format Preprint
id arxiv_https___arxiv_org_abs_2603_12234
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Thermalisation as Diffusion in Hilbert Space
Lunkin, Aleksey
Disordered Systems and Neural Networks
Statistical Mechanics
Quantum Physics
We develop a microscopic theory of thermalisation for a thermometer coupled to a many-body bath beyond standard Markovian and Fermi-golden-rule assumptions. By modeling interaction matrix elements in the non-interacting basis as independent random variables, we derive a diffusion-propagator expression for the reduced dynamics and show that relaxation is controlled by the distribution of interaction-induced level broadenings. The theory predicts a thermalisation timescale set by the inverse typical broadening and yields a non-Markovian generalization of global balance. Exact-diagonalization tests for heavy-tailed L{é}vy couplings, an all-to-all transverse-field Ising model, and the one-dimensional Imbrie model show good agreement with these predictions.
title Thermalisation as Diffusion in Hilbert Space
topic Disordered Systems and Neural Networks
Statistical Mechanics
Quantum Physics
url https://arxiv.org/abs/2603.12234