The finite basis problem for monoids of triangular boolean matrices (Algebraic Systems, Formal Languages and Conventional and Unconventional Computation Theory)
Mikhail Vladimirovich Volkov, Ian Goldberg · Kyoto University Research Information Repository (Kyoto University) · 2004
We show that the monoid of all $n\cross n$ upper triangular boolean matrices has no finite identity basis whenever $n>3$ .The identities of its submonoid consisting of matrices in which all diagonal entries are 1 possess a finite basis if and only if $n\leq 4$ .