New Degree Spectra of Abelian Groups
Alexander Melnikov · Notre Dame Journal of Formal Logic · 2017
We show that for every computable ordinal of the form β=δ+2n+1>1, where δ is zero or a limit ordinal and n∈ω, there exists a torsion-free abelian group having an X-computable copy if and only if X is nonlowβ.