A Characterization of Ext(g, Z) Assuming (v = L)
نویسندگان
چکیده
In this paper we complete the characterization of Ext(G, Z) for any torsion-free abelian group G assuming Gödel’s axiom of constructibility plus there is no weakly compact cardinal. In particular, we prove in (V = L) that, for a singular cardinal ν of uncountable cofinality which is less than the first weakly compact cardinal and for every sequence of cardinals (νp : p ∈ Π) satisfying νp ≤ 2 , there is a torsion-free abelian group G of size ν such that νp equals the p-rank of Ext(G, Z) for every prime p and 2 is the torsion-free rank of Ext(G, Z).
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