PSEUDOVARIETY JOINS INVOLVING ${\mathscr J}$ -TRIVIAL SEMIGROUPS
Jorge Almeida, Assis Azevedo, Marc Zeitoun · International Journal of Algebra and Computation · 1999
J. Rhodes asked during the Chico Conference in 1986 for the calculation of joins of semigroup pseudovarieties. This paper proves that the join J∨H of the pseudovariety J of [Formula: see text]-trivial semigroups and of any 2-strongly decidable pseudovariety V of of completely regular semigroups is decidable. This problem was proposed by the first author for V=G, the pseudovariety of finite groups.