On Pointlike Sets and Joins of Pseudovarieties
Benjamin Steinberg · International Journal of Algebra and Computation · 1998
In this paper we give a criterion for a subset of a semigroup to be pointlike for the join or wreath product of two pseudovarieties. As a consequence we obtain a criterion for membership in the join of two pseudovarieties. Applications include pointlikes for J ∨ G.