The Tambara-Yamagami calculus and finite semigroups

Abstract

Tambara-Yamagami categories are among the simplest fusion categories beyond the pointed case: one adds a single noninvertible simple object to a finite group of invertible ones. We ask what remains of their (diagrammatic) calculus when the group is replaced by a finite semigroup, and develop the resulting (diagrammatic) calculus.

arXiv comment63 pages, many figures, comments welcome