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arXiv 2105.08596hep-thcond-mat.stat-mech
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共形场论中对称分辨的相对熵和距离

Symmetry resolved relative entropies and distances in conformal field theory

Luca Capizzi, Pasquale Calabrese

摘要:

本文发展了一种系统的方法来计算具有U(1)对称性的1 + 1维共形场论中不同对称扇区中激发态的子系统约化密度矩阵的子系统迹距和相对熵。给出了一般整数$n$的荷电矩的解析表达式,该表达式对应于相对熵和距离的分辨率。对于相对熵,这些公式是可操作的,并且在大多数情况下可以求出$n=1$的解析延拓。相反,对于距离,随着$n$的增加,相应的带电矩很快变得不可处理。一个值得注意的结果是,相对熵和距离对于所有对称扇区都是相同的,即它们像熵一样满足纠缠均分。此外,我们利用复合扭曲场的OPE展开,提供非常普遍的结果时,子系统是远远小于总系统。我们专注于无质量的紧凑玻色子和我们的结果进行了测试,对精确的数值计算在XX自旋链。

英文摘要:

We develop a systematic approach to compute the subsystem trace distances and relative entropies for subsystem reduced density matrices associated to excited states in different symmetry sectors of a 1+1 dimensional conformal field theory having an internal U(1) symmetry. We provide analytic expressions for the charged moments corresponding to the resolution of both relative entropies and distances for general integer $n$. For the relative entropies, these formulas are manageable and the analytic continuation to $n=1$ can be worked out in most of the cases. Conversely, for the distances the corresponding charged moments become soon untreatable as $n$ increases. A remarkable result is that relative entropies and distances are the same for all symmetry sectors, i.e. they satisfy entanglement equipartition, like the entropies. Moreover, we exploit the OPE expansion of composite twist fields, to provide very general results when the subsystem is much smaller than the total system. We focus on the massless compact boson and our results are tested against exact numerical calculations in the XX spin chain.

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