Semigroups with zero whose idempotents form a subsemigroup
Gracinda M. S. Gomes, John M Howie · Proceedings of the Royal Society of Edinburgh Section A Mathematics · 1998
The structure of a categorical,E*-dense,E*-unitaryE-semigroupSis elucidated in terms of a ‘B-quiver’, whereBis a primitive inverse semigroup. In the case whereSis strongly categorical,Bis a Brandt semigroup. A covering theorem is also proved, to the effect that every categoricalE*-denseE-semigroup has a cover which is a categorical,E*-dense,E*-unitaryE-semigroup.