On the degrees of constructively immune sets

Abstract

Xiang Li (1983) introduced what are now called constructively immune sets as an effective version of immunity. Such have been studied in relation to randomness and minimal indices, and we add another application area: numberings of the rationals. We also investigate the Turing degrees of constructively immune sets and the closely related $\Sigma^0_1$-dense sets of Ferbus-Zanda and Grigorieff (2008).