More on bases of uncountable free abelian groups
journal contributionposted on 20.09.2020, 01:54 by Noam Greenberg, Linus 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.