Separable mixed groups
Isotype subgroups of mixed groups
In this paper, we initiate the study of various classes of isotype subgroups of global mixed groups. Our goal is to advance the theory of -isotype subgroups to a level comparable to its status in the simpler contexts of torsion-free and -local mixed groups. Given the history of those theories, one anticipates that definitive results are to be found only when attention is restricted to global -groups, the prototype being global groups with decomposition bases. A large portion of this paper is...
Isotype knice subgroups of global Warfield groups
If is an isotype knice subgroup of a global Warfield group , we introduce the notion of a -subgroup to obtain various necessary and sufficient conditions on the quotient group in order for itself to be a global Warfield group. Our main theorem is that is a global Warfield group if and only if possesses an -family of almost strongly separable -subgroups. By an -family we mean an Axiom 3 family in the strong sense of P. Hill. As a corollary to the main theorem, we are able to characterize...
The nonseparability of simply presented mixed groups
It is demonstrated that an isotype subgroup of a simply presented abelian group can be simply presented without being a separable subgroup. In particular, the conjecture based on a variety of special cases that Warfield groups are absolutely separable is disproved.
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