More on bases of uncountable free abelian groups
journal contributionposted on 20.09.2020, 01:54 by Noam Greenberg, Linus RichterLinus Richter, Saharon Shelah, Daniel Turetsky
We extend results found by Greenberg, Turetsky, and Westrick in  and investigate effective properties of bases of uncountable free abelian groups. Assuming V = L, we show that if κ is a regular uncountable cardinal and X is a ∆11(Lκ) subset of κ, then there is a κ-computable free abelian group whose bases cannot be effectively computed by X. Unlike in , we give a direct construction.