Abstract (EN):
Based on the operators h(n) and i(n) and their duals (H-n) over bar, and (i(n)) over bar defined on the free semigroup X+ for a nonempty set X by Gerhard and Petrich, we introduce here the operators theta(pq) which are proved to be homomorphisms of X+ onto certain subsets of X+ with suitable multiplication. These operators induce fully invariant congruences on X+ corresponding to most of the varieties of bands if X is countably infinite. Variants of operators lambda and rho introduced by the cited authors are used here to elucidate the structure of relatively free bands for most band varieties in conjunction with the operators theta(pq). The few remaining varieties are treated separately.
Idioma:
Inglês
Tipo (Avaliação Docente):
Científica
Nº de páginas:
23