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arXiv · 1503.07292

Symmetry protection of critical phases and global anomaly in $1+1$ dimensions

Shunsuke C. Furuya·Masaki Oshikawa
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Abstract

We derive a selection rule among the $(1+1)$-dimensional SU(2) Wess-Zumino-Witten theories, based on the global anomaly of the discrete $\mathbb{Z}_2$ symmetry found by Gepner and Witten. In the presence of both the SU(2) and $\mathbb{Z}_2$ symmetries, a renormalization-group flow is possible between level-$k$ and level-$k'$ Wess-Zumino-Witten theories only if $k\equiv k' \mod{2}$. This classifies the Lorentz-invariant, SU(2)-symmetric critical behavior into two "symmetry-protected" categories corresponding to even and odd levels,restricting possible gapless critical behavior of translation-invariant quantum spin chains.

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Shunsuke C. Furuya, Masaki Oshikawa. 2017-01-13. Symmetry protection of critical phases and global anomaly in $1+1$ dimensions. https://doi.org/10.1103/physrevlett.118.021601

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