Hierarchy of Computably Enumerable Degrees II
Rodney G. Downey, Noam Greenberg, Ellen Hammatt · New Zealand journal of mathematics · 2021
A transfinite hierarchy of Turing degrees of c.e.\ sets has been used to calibrate the dynamics of families of constructions in computability theory, and yields natural definability results. We review the main results of the area, and discuss splittings of c.e.\ degrees, and finding maximal degrees in upper cones.