Almost all minimal idempotent varieties are congruence modular. Algebra Universalis 44

Abstract. We show that, up to term equivalence, the only mini-mal idempotent varieties that are not congruence modular are the variety of sets and the variety of semilattices. From this it fol-lows that a minimal idempotent variety that is not congruence distributive is term equivalent to the variety of sets, the variety of semilattices, or a variety of ane modules over a simple ring. 1