On coherent systems of projections for $\aleph_1$ separable groups

by Eklof and Mekler and Shelah. [EMSh:426]
Communications in Algebra, 1993
It is proved consistent with either CH or the negation of CH that there is an aleph_1-separable group of cardinality aleph_1 which does not have a coherent system of projections. It had previously been shown that it is consistent with not CH that every aleph_1-separable group of cardinality aleph_1 does have a coherent system of projections.


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