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• # Artykuł - szczegóły

## Fundamenta Mathematicae

2007 | 193 | 2 | 141-151

## A characterization of Ext(G,ℤ) assuming (V = L)

EN

### Abstrakty

EN
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 $(ν_{p}: p ∈ Π)$ of cardinals satisfying $ν_{p} ≤ 2^{ν}$ (where Π is the set of all primes), there is a torsion-free abelian group G of size ν such that $ν_{p}$ equals the p-rank of Ext(G,ℤ) for every prime p and $2^{ν}$ is the torsion-free rank of Ext(G,ℤ).

141-151

wydano
2007

### Twórcy

autor
• Department of Mathematics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
• Rutgers University, New Brunswick, NJ 08903, U.S.A.
autor
• Department of Mathematics, University of Duisburg-Essen, 45117 Essen, Germany
• Department of Mathematics, University of Hawaii, 2565 McCarthy Mall, Honolulu, HI 96822-2273, U.S.A.