Hostname: page-component-84b7d79bbc-lrf7s Total loading time: 0 Render date: 2024-07-29T13:24:33.542Z Has data issue: false hasContentIssue false

Rice Theorems for ∑n-1 Sets

Published online by Cambridge University Press:  20 November 2018

Nancy Johnson*
Affiliation:
Chicago State University, Chicago, Illinois
Rights & Permissions [Opens in a new window]

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

In [3] Hay proves generalizations of Rice's Theorem and the Rice-Shapiro Theorem for differences of recursively enumerable sets (d.r.e. sets). The original Rice Theorem [5, p. 3G4, Corollary B] says that the index set of a class C of r.e. sets is recursive if and only if C is empty or C contains all r.e. sets. The Rice-Shapiro Theorem conjectured by Rice [5] and proved independently by McNaughton, Shapiro, and Myhill [4] says that the index set of a class C of r.e. sets is r.e. if and only if C is empty or C consists of all r.e. sets which extend some element of a canonically enumerable class of finite sets. Since a d.r.e. set is a difference of r.e. sets, a d.r.e. set has an index associated with it, namely, the pair of indices of the r.e. sets of which it is the difference.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1977

References

1. Ershov, Yu. L., A hierarchy of sets, I, Algebra and Logic 7 (1968), 2543.Google Scholar
2. Hay, L., A discrete chain of degrees of index sets, J. Symb. Log. 37 (1972), 139149.Google Scholar
3. Hay, L. Rice theorems for d.r.e. sets, Can. J. Math. 27 (1975), 352365.Google Scholar
4. Myhill, J., A fixed point theorem in recursion theory, Abstract, J. Symb. Log. 20 (1955), 205.Google Scholar
5. Rice, H. G., Classes of recursively enumerable sets and their key arrays, Trans. Amer. Math. Soc. 74 (1953), 358366.Google Scholar
6. Rogers, H., Jr., Computing degrees of unsolvability, Math. Annalen 138 (1959), 125140.Google Scholar