ON A CLASS OF SEMIGROUP PSEUDOVARIETIES WITHOUT FINITE PSEUDOIDENTITY BASIS
Mikhail Vladimirovich Volkov · International Journal of Algebra and Computation · 1995
We show that every semigroup pseudovariety [Formula: see text] containing a group not in the subpseudovariety generated by all idempotent generated members of [Formula: see text] has no finite basis of pseudoidentities provided the five-element idempotent generated 0-simple semigroup lies in [Formula: see text]. This gives, in particular, a counterexample to a conjecture by J. Almeida.