On a Problem of A. Nagy

Abstract

If the congruences of a semigroup are commutative, we say that the semigroup is permutable. In a previous paper, A. Nagy showed that every permutable semigroup satisfying an arbitrary non-trivial permutation identity is medial or an ideal extension of a rectangular band by a non-trivial commutative nil semigroup. The author raised the following problem: Is every permutable semigroup satisfying a non-trivial permutation identity medial? In present paper we give a positive answer for this problem.