paper

Quantized topological terms in weak-coupling gauge theories with symmetry and their connection to symmetry enriched topological phases

arXiv:1212.1827 · doi:10.1103/PhysRevB.87.165107

Abstract

We study the quantized topological terms in a weak-coupling gauge theory with gauge group and a global symmetry in space-time dimensions. We show that the quantized topological terms are classified by a pair , where is an extension of by and an element in group cohomology $\cH^d(G,\R/\Z)$. When and/or when is finite, the weak-coupling gauge theories with quantized topological terms describe gapped symmetry enriched topological (SET) phases (i.e. gapped long-range entangled phases with symmetry). Thus, those SET phases are classified by $\cH^d(G,\R/\Z)$, where . We also apply our theory to a simple case , which leads to 12 different SET phases in 2+1D, where quasiparticles have different patterns of fractional quantum numbers and fractional statistics. If the weak-coupling gauge theories are gapless, then the different quantized topological terms may describe different gapless phases of the gauge theories with a symmetry , which may lead to different fractionalizations of quantum numbers and different fractional statistics (if in 2+1D).

13 pages, 2 figures, PRB accepted version with added clarification on obtaining G_s charge for a given PSG with non-trivial topological terms. arXiv admin note: text overlap with arXiv:1301.7675

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