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arXiv · 2103.05035

Topological terms of (2+1)d flag-manifold sigma models

Ryohei Kobayashi·Yasunori Lee·Ken Shiozaki·Yuya Tanizaki
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Abstract

We examine topological terms of $(2+1)$d sigma models and their consequences in the light of classifications of invertible quantum field theories utilizing bordism groups. In particular, we study the possible topological terms for the $U(N)/U(1)^N$ flag-manifold sigma model in detail. We argue that the Hopf-like term is absent, contrary to the expectation from a nontrivial homotopy group $\pi_3(U(N)/U(1)^N)=\mathbb{Z}$, and thus skyrmions cannot become anyons with arbitrary statistics. Instead, we find that there exist ${N(N-1)\over 2}-1$ types of Chern-Simons terms, some of which can turn skyrmions into fermions, and we write down explicit forms of effective Lagrangians.

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Ryohei Kobayashi, Yasunori Lee, Ken Shiozaki, Yuya Tanizaki. 2021-03-08. Topological terms of (2+1)d flag-manifold sigma models. https://doi.org/10.1007/jhep08(2021)075

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