The independence of the Whitehead problem from ZFC
Richard J. Dean · cIRcle (University of British Columbia) · 2010
An abelian group G is called a W-group if Ext(G,Z) = 0. Whitehead's problem asks which groups are W-groups. Saharon Shelah proved that the answer to Whitehead's problem, for groups of cardinality ω₁ , is independent of the axioms of Zermelo-Frankel set theory with the axiom of choice. This thesis gives a complete and detailed proof, based on Shelah's proof, of this independence result.