Congruence permutable MS-algebras

We characterize the congruence permutable MS-algebras in a result analogous to that of Nachbin for distributive lattices. In our main result we prove, among other things, that the congruence permutability of an MS-algebra L is equivalent to the existence of two binary operations in L which satisfy certain equational properties. We show that the class of all congruence permutable MS-algebras with these additional operations forms an equational class. Finally we give a Mal’cev term for this new variety. Presented by J. Berman. Received May 12, 2005; accepted in final form November 5, 2005. Research supported by ANPCyT (Contrato Préstamo BID 1201/OC-AR) and SECyT (UNC)