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arXiv 2406.08730cond-mat.stat-mech
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Heisenberg链中弱可积性破缺微扰的有限尺寸生成元

Finite-size generators for weak integrability breaking perturbations in the Heisenberg chain

Sara Vanovac, Federica Maria Surace, Olexei Motrunich

AI总结:

针对周期边界有限Heisenberg链,本文借助绝热规范势研究弱可积性破缺微扰的生成元,揭示boosted与双局域生成元的精确关系及其准局域性,并提出严格局域变体。

摘要:

一个可积模型在受到特殊的“弱可积性破缺”微扰时,其热化所处的时间尺度远长于Fermi黄金定则所预测的时间尺度。近来,人们系统构建了一类基于可积链所谓长程形变的此类微扰。这些微扰是在某个小参数展开中对长程形变进行截断而得到的,可视为由短程可积模型的幺正旋转所产生。对于无限系统,已知存在若干弱微扰的“生成元”(广延局域、boosted和双局域算符)。本工作的主要目标是理解具有周期边界的有限系统中适当的生成元,因为在此类情形下尚不知道boosted和双局域算符的简单对应物。我们通过研究绝热规范势(AGP)的结构来处理这一问题;AGP是有限链中此类生成元的代理量,最初被引入作为量子混沌的一种高度敏感度量。我们证明了boosted类与双局域类生成元的AGP之间存在精确关系,并注意到boost的对应物在有限系统中似乎不具有闭合解析形式,但仍表现出准局域性。我们还引入并研究了弱可积性破缺微扰的严格局域变体。

英文摘要:

An integrable model perturbed by special ''weak integrability-breaking'' perturbations thermalizes at timescales much longer than predicted by Fermi's golden rule. Recently, a systematic construction of such perturbations based on the so-called long-range deformations of integrable chains was formulated. These perturbations, obtained as truncations of the long-range deformations in some small parameter expansions, can be viewed as produced by unitary rotations of the short-range integrable models. For infinite systems, several ''generators'' (extensive local, boosted, and bilocal operators) of weak perturbations are known. The main aim of this work is to understand the appropriate generators in finite systems with periodic boundaries since simple counterparts to boosted and bilocal operators are not known in such cases. We approach this by studying the structure of the adiabatic gauge potential (AGP), a proxy for such generators in finite chains, which was originally introduced as a very sensitive measure of quantum chaos. We prove an exact relation between the AGPs for the boosted and bilocal classes of generators and note that the counterpart to boost does not seem to have a closed analytic form in finite systems but shows quasi-locality nonetheless. We also introduce and study strictly local variants of weak integrability-breaking perturbations.

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