Semiclassical analytical solutions of the eigenstate thermalization hypothesis in a quantum billiard

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Hauptverfasser: Ye, Yaoqi, Lin, Chengkai, Wang, Xiao
Format: Preprint
Veröffentlicht: 2025
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author Ye, Yaoqi
Lin, Chengkai
Wang, Xiao
author_facet Ye, Yaoqi
Lin, Chengkai
Wang, Xiao
contents We derive semiclassical analytical solutions for both the diagonal and off-diagonal functions in the eigenstate thermalization hypothesis (ETH) in a quarter-stadium quantum billiard. For a representative observable, we obtain an explicit expression and an asymptotic closed-form solution that naturally separate into a local contribution and a phase-space correlation term. These analytical results predict the band structure of the observable matrix, including its bandwidth and scaling behavior. We further demonstrate that our analytical formula is equivalent to the prediction of Berry's conjecture. Supported by numerical evidence, we show that Berry's conjecture captures the energetic long-wavelength behavior in the space of eigenstates, while our analytical solution describes the asymptotic behavior of the f function in the semiclassical limit. Finally, by revealing the connection between the bandwidth scaling and the underlying classical dynamics, our results suggest that the ETH carries important physical implications in single-particle and few-body systems, where "thermalization" manifests as the loss of information about initial conditions.
format Preprint
id arxiv_https___arxiv_org_abs_2510_12517
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Semiclassical analytical solutions of the eigenstate thermalization hypothesis in a quantum billiard
Ye, Yaoqi
Lin, Chengkai
Wang, Xiao
Quantum Physics
Statistical Mechanics
Chaotic Dynamics
We derive semiclassical analytical solutions for both the diagonal and off-diagonal functions in the eigenstate thermalization hypothesis (ETH) in a quarter-stadium quantum billiard. For a representative observable, we obtain an explicit expression and an asymptotic closed-form solution that naturally separate into a local contribution and a phase-space correlation term. These analytical results predict the band structure of the observable matrix, including its bandwidth and scaling behavior. We further demonstrate that our analytical formula is equivalent to the prediction of Berry's conjecture. Supported by numerical evidence, we show that Berry's conjecture captures the energetic long-wavelength behavior in the space of eigenstates, while our analytical solution describes the asymptotic behavior of the f function in the semiclassical limit. Finally, by revealing the connection between the bandwidth scaling and the underlying classical dynamics, our results suggest that the ETH carries important physical implications in single-particle and few-body systems, where "thermalization" manifests as the loss of information about initial conditions.
title Semiclassical analytical solutions of the eigenstate thermalization hypothesis in a quantum billiard
topic Quantum Physics
Statistical Mechanics
Chaotic Dynamics
url https://arxiv.org/abs/2510.12517