ON SUPERSETS OF NON-LOW SETS
Klaus Ambos‐Spies, Rodney G. Downey, Martin Monath · Journal of Symbolic Logic · 2021
Abstract We solve a longstanding question of Soare by showing that if ${\mathbf d}$ is a non-low $_2$ computably enumerable degree then ${\mathbf d}$ contains a c.e. set with no r-maximal c.e. superset.