On The Schützenberger Product of Three Copies of a Free Group
Orlando Neto, Helena Sezinando · International Journal of Algebra and Computation · 1998
We show that the Schützenberger product "cut down to generators" of three copies of a free group is a relatively free monoid with involution. We show that its set of idempotents has a natural structure of a semilattice. This semilattice is naturally isomorphic to the semilattice of idempotents of a free inverse monoid.