Permitting, forcing, and copying of a given recursive relation
Let \(\mathcal A\) be a recursive structure for a language \(L\) and \(R\) be a relation on \(\mathcal A\). The authors give conditions under which this relation can be made \(\alpha\)-r.e. in Ershov's hierarchy of \(\Delta^0_2\)-sets in an appropriate recursive copy of \(\mathcal A\).
scientific article; zbMATH DE number 1054202