paper

Anomaly of -Dimensional Symmetry-Enriched Topological Order from -Dimensional Topological Quantum Field Theory

arXiv:2210.02444 · doi:10.21468/SciPostPhys.15.1.004

Abstract

Symmetry acting on a (2+1) topological order can be anomalous in the sense that they possess an obstruction to being realized as a purely (2+1) on-site symmetry. In this paper, we develop a (3+1) topological quantum field theory to calculate the anomaly indicators of a (2+1) topological order with a general symmetry group , which may be discrete or continuous, Abelian or non-Abelian, contain anti-unitary elements or not, and permute anyons or not. These anomaly indicators are partition functions of the (3+1) topological quantum field theory on a specific manifold equipped with some -bundle, and they are expressed using the data characterizing the topological order and the symmetry actions. Our framework is applied to derive the anomaly indicators for various symmetry groups, including , , , , , etc, where and denote a unitary and anti-unitary order-2 group, respectively, and denotes a symmetry group such that elements in with determinant are anti-unitary. In particular, we demonstrate that some anomaly of and exhibit symmetry-enforced gaplessness, i.e., they cannot be realized by any symmetry-enriched topological order. As a byproduct, for symmetric topological orders, we derive their Hall conductance.

Recipe of calculating the partition function involving continuous symmetries added, together with extra examples

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