On the Problem of Definability of the Computably Enumerable Degrees in the Difference Hierarchy
M. M. Arslanov, Mars M. Yamaleev · Lobachevskii Journal of Mathematics · 2018
Questions of definability of computably enumerable degrees in the difference hierarchy (degrees of sets from finite levels of the Ershov difference hierarchy) are studied. Several approaches to the solution of this problem are outlined.