Grothendieck rings of near-Tambara--Yamagami fusion categories

We determine the Grothendieck rings of fusion categories over $\mathcal{C}$ containing a nonpointed Tambara--Yamagami fusion subcategory and exactly one further simple object. The subcategory necessarily has rank five, its invertible objects form the Klein four-group, and the coefficient $κ$ of the additional simple object in its tensor square belongs to $\{0,2,7\}$. Each of these three based rings is categorifiable. For $κ=0$, every category belongs, up to tensor equivalence, to the rank-one odd-component extension list of Choi--Lu--Sun. For $κ=2$ we construct an explicit unitary group-theoretical realization, and for $κ=7$ a realization is $\rm{Rep}(\rm{PSU}(3,2))$.

Authors

Publication Details

Journal
arXiv (Cornell University)
Published
2026-10-26
DOI
https://doi.org/10.48550/arxiv.2610.35574
Primary Topic
Algebraic structures and combinatorial models
Type
preprint
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preprint

Grothendieck rings of near-Tambara--Yamagami fusion categories

Sébastien Palcoux, Jingcheng Dong, Kai Wang
arXiv (Cornell University)
Algebraic structures and combinatorial models
preprint

Grothendieck rings of near-Tambara--Yamagami fusion categories

Sébastien Palcoux, Jingcheng Dong, Kai Wang
preprint en

Abstract

We determine the Grothendieck rings of fusion categories over $\mathcal{C}$ containing a nonpointed Tambara--Yamagami fusion subcategory and exactly one further simple object. The subcategory necessarily has rank five, its invertible objects form the Klein four-group, and the coefficient $κ$ of the additional simple object in its tensor square belongs to $\{0,2,7\}$. Each of these three based rings is categorifiable. For $κ=0$, every category belongs, up to tensor equivalence, to the rank-one odd-component extension list of Choi--Lu--Sun. For $κ=2$ we construct an explicit unitary group-theoretical realization, and for $κ=7$ a realization is $\rm{Rep}(\rm{PSU}(3,2))$.

arXiv (Cornell University)
Algebraic structures and combinatorial models
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Grothendieck rings of near-Tambara--Yamagami fusion categories — Sébastien Palcoux, Jingcheng Dong, et al. · arXiv (Cornell University) (2026) | TGRS Research Map | TGRS