Twisted locality-preserving automorphisms, anomaly index, and generalized Lieb-Schultz-Mattis theorems with anti-unitary symmetries

• URL: http://arxiv.org/abs/2510.06555v1
• Date: Wed, 08 Oct 2025 01:17:21 GMT
• Title: Twisted locality-preserving automorphisms, anomaly index, and generalized Lieb-Schultz-Mattis theorems with anti-unitary symmetries
• Authors: Ruizhi Liu, Jinmin Yi, Liujun Zou,
• Abstract summary: We show that an anomalous symmetry leads to multiple Lieb-Schultz-Matttis-type theorems.<n>We further deduce that any state with an anomalous symmetry must have long-range entanglement.<n>For Hamiltonians with only two-spin interactions, the last theorem holds if the interactions decay faster than $1/r2$, where $r$ is the distance between the two interacting spins.
• Score: 1.0960289997471084
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Symmetries and their anomalies are powerful tools to understand quantum matter. In this work, for quantum spin chains, we define twisted locality-preserving automorphisms and their Gross-Nesme-Vogts-Werner indices, which provide a unified framework to describe both unitary and anti-unitary symmetries, on-site and non-on-site symmetries, and internal and translation symmetries. For a symmetry $G$ with actions given by twisted locality-preserving automorphisms, we give a microscopic definition of its anomaly index, which is an element in $H^3_\varphi(G; U(1))$, where the subscript $\varphi$ means that anti-unitary elements of $G$ act on $U(1)$ by complex conjugation. We show that an anomalous symmetry leads to multiple Lieb-Schultz-Matttis-type theorems. In particular, any state with an anomalous symmetry must either have long-range correlation or violate the entanglement area law. Based on this theorem, we further deduce that any state with an anomalous symmetry must have long-range entanglement, and any Hamiltonian that has an anomalous symmetry cannot have a unique gapped symmetric ground state, as long as the interactions in the Hamiltonian decay fast enough as the range of the interaction increases. For Hamiltonians with only two-spin interactions, the last theorem holds if the interactions decay faster than $1/r^2$, where $r$ is the distance between the two interacting spins. We demonstrate these general theorems in various concrete examples.

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