Some Studies On Union Of Groups And Congruences

In the subvariety lattice of completely regular semigroups, the join of the or-thogroup variety and the cryptogroup variety is determined.By using a construction theorem of cryptogroups, we describe congruences con-tained in the Green’s relation (?) on a cryptogroup. Then several classes of least congruences on cryptogroup are determined.This thesis contains three chapters.In Chapter1, we introduce some definitions and lemmas, fix some notation which is used in the remaining part.In Chapter2, we obtain an identity for the variety (?).In Chapter3, some classes of least congruences contained in the Green’s relation (?) on a cryptogroup is described.