Scaling of free cumulants in closed system-bath setups

Fuente: arXiv
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Main Authors: Füllgraf, Merlin, Gemmer, Jochen, Wang, Jiaozi
Format: Preprint
Published: 2025
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author Füllgraf, Merlin
Gemmer, Jochen
Wang, Jiaozi
author_facet Füllgraf, Merlin
Gemmer, Jochen
Wang, Jiaozi
contents The Eigenstate Thermalization Hypothesis (ETH) has been established as a cornerstone for understanding thermalization in quantum many-body systems. Recently, there has been growing interest in the full ETH, which extends the framework of the conventional ETH and postulates a smooth function to describe the multi-point correlations among matrix elements. Within this framework, free cumulants play a central role, and most previous studies have primarily focused on closed systems. In this paper, we extend the analysis to a system-bath setup, considering both an idealized case with a random-matrix bath and a more realistic scenario where the bath is modeled as a defect Ising chain. In both cases, we uncover a universal scaling of the microcanonical free cumulants of observables associated with the central system Hamiltonian with respect to the interaction strength. Furthermore we establish a connection between this scaling behavior and the thermalization dynamics of the thermal free cumulants of corresponding observables.
format Preprint
id arxiv_https___arxiv_org_abs_2511_11333
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Scaling of free cumulants in closed system-bath setups
Füllgraf, Merlin
Gemmer, Jochen
Wang, Jiaozi
Statistical Mechanics
Quantum Physics
The Eigenstate Thermalization Hypothesis (ETH) has been established as a cornerstone for understanding thermalization in quantum many-body systems. Recently, there has been growing interest in the full ETH, which extends the framework of the conventional ETH and postulates a smooth function to describe the multi-point correlations among matrix elements. Within this framework, free cumulants play a central role, and most previous studies have primarily focused on closed systems. In this paper, we extend the analysis to a system-bath setup, considering both an idealized case with a random-matrix bath and a more realistic scenario where the bath is modeled as a defect Ising chain. In both cases, we uncover a universal scaling of the microcanonical free cumulants of observables associated with the central system Hamiltonian with respect to the interaction strength. Furthermore we establish a connection between this scaling behavior and the thermalization dynamics of the thermal free cumulants of corresponding observables.
title Scaling of free cumulants in closed system-bath setups
topic Statistical Mechanics
Quantum Physics
url https://arxiv.org/abs/2511.11333