POWER COMMUTATIVE SEMIGROUPS AND THEIR CORRESPONDING RATIONAL LANGUAGES

A characterization of finite semigroups (power commutative semigroups) satisfying the equation (xy);The variety of semigroups with central idempotents is shown to be generated by semigroups that have exactly 0 and 1 as idempotents. From this, the class of rational languages corresponding to semigroups with central idempotents is shown to be the Boolean closure of languages of the form L...