Symmetric implication zroupoids and identities of Bol–Moufang type

Abstract

An algebra A= ⟨ A, → , 0 ⟩ , where → is binary and 0 is a constant, is called an implication zroupoid (I-zroupoid, for short) if A satisfies the identities: (I): (x→y)→z≈((z′→x)→(y→z)′)′, and (I0): 0 ′ ′≈ 0 , where x′: = x→ 0. An implication zroupoid is symmetric if it satisfies the identities: x′ ′≈ x and (x→y′)′≈(y→x′)′. An identity is of Bol–Moufang type if it contains only one binary operation symbol, one of its three variables occurs twice on each side, each of the other two variables occurs once on each side, and the variables occur in the same (alphabetical) order on both sides of the identity. In this paper, we will present a systematic analysis of all 60 identities of Bol–Moufang type in the variety S of symmetric I-zroupoids. We show that 47 of the subvarieties of S, defined by the identities of Bol–Moufang type, are equal to the variety SL of ∨ -semilattices with the least element 0 and one of others is equal to S. Of the remaining 12, there are only three distinct ones. We also give an explicit description of the poset of the (distinct) subvarieties of S of Bol–Moufang type.