MAXIMAL CLASSES OF ABELIAN GROUPS ARISING FROM THE ISOMORPHISM G ≅ T[EXT(X,G)]

Abstract

It is well known that the class R of all reduced torsion groups has the property that G ≅ T[Ext(Q/Z,G)] for every G in R. In this paper we prove the existence of other classes K of groups having the property that a group X exists such that G ≅ T[Ext(X,G)] for every group G in H. Furthermore these classes turn out to be maximal with respect to this property.