Closed left-r.e. sets
Sanjay K. Jain, Frank Stephan, Jason Teutsch · Computability · 2016
A set is called r-closed left-r.e. iff every set r-reducible to it is also a left-r.e. set. It is shown that some but not all left-r.e. cohesive sets are many–one closed left-r.e. sets. Ascending reductions are many–one reductions via an ascending fu