On r.e. inseparability of CPO index sets

In this paper the r.e. inseparability and the effective r.e. inseparability of index sets under certain indexings of the computable elements of an effective cpo are studied. As a consequence of the main result on effective r.e. inseparability we obtain a generalization of a theorem by McNaughton. As a further application we obtain generalizations of results by Myhill/Dekker on the productivity of certain index sets. From this we infer the generalization of theorems by Rice/Shapiro/McNaughton/Myhill and Myhill/Shepherdson. This demonstrates the importance of the r.e. inseparability notion.