A nonfinitely based semigroup of triangular matrices

Abstract

A new sufficient condition under which a semigroup admits no finite identity basis has been recently suggested in a joint paper by Karl Auinger, Yuzhu Chen, Xun Hu, Yanfeng Luo, and the author (see http://arxiv.org/abs/1405.0783). Here we apply this condition to show the absence of a finite identity basis for the semigroup ${\mathrm{UT}}_3(\mathbb{R})$ of all upper triangular real $3\times 3$-matrices with 0s and/or 1s on the main diagonal. The result holds also for the case when ${\mathrm{UT}}_3(\mathbb{R})$ is considered as an involution semigroup under the reflection with respect to the secondary diagonal.

11 pages; submitted to the proceedings of the International Conference on Semigroups, Algebras and Operator Theory held at the Cochin University of Science and Technology (Kerala, India) in February 2014