English

Gauging the Categorical Connes' $\tilde{\chi}(M)$

Operator Algebras 2026-04-24 v1 Category Theory Quantum Algebra

Abstract

We prove that if a finite group GG acts outerly on a McDuff II1\rm II_1 factor MM, then Rep(G/KL)\mathsf{Rep}(G/KL) is a braided monoidal full subcategory of the categorical Connes' χ~(MG)\tilde{\chi}(M\rtimes G) defined in arXiv:2111.06378, where KK and LL are the centrally trivial and approximately inner parts in GG respectively. When LL is trivial, we give an explicit formula for the G/KG/K-gauging procedure on χ~(MG)\tilde{\chi}(M\rtimes G). This is the categorical generalization of Connes' short exact sequence on χ(MG)\chi(M\rtimes G). Using this machinery, for any finite group GG, we construct a McDuff II1\rm II_1 factor MM, whose χ~(M)\tilde{\chi}(M) is braided equivalent to Rep(G)\mathsf{Rep}(G). This is the first example of a braided fusion category which is not modular as χ~\tilde\chi.

Keywords

Cite

@article{arxiv.2604.21833,
  title  = {Gauging the Categorical Connes' $\tilde{\chi}(M)$},
  author = {Quan Chen},
  journal= {arXiv preprint arXiv:2604.21833},
  year   = {2026}
}

Comments

36 pages, several tikz figures

R2 v1 2026-07-01T12:32:45.278Z