Identities in twisted Brauer monoids

Abstract

We show that it is co-NP-hard to check whether a given semigroup identity holds in the twisted Brauer monoid ${\mathcal{B}}_n^{\tau }$ with $n\ge 5$.

20 pages, 5 figures. In v2, several typos and inaccuracies are corrected, and a few suggestions by the anonymous referee are implemented