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arXiv · 2411.05067

On Unitary 2-Group Symmetries

Thomas Bartsch
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Abstract

Global internal symmetries act unitarily on local observables or states of a quantum system. In this note, we aim to generalise this statement to extended observables by considering unitary actions of finite global 2-group symmetries $\mathcal{G}$ on line operators. We propose that the latter transform in unitary 2-representations of $\mathcal{G}$, which we classify up to unitary equivalence. Our results recover the known classification of ordinary 2-representations of finite 2-groups, but provide additional data interpreted as a type of reflection anomaly for $\mathcal{G}$.

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Thomas Bartsch. 2024-11-07. On Unitary 2-Group Symmetries. https://arxiv.org/abs/2411.05067

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