Abstract
In [1], p. 171, Sacks asks (question (Q5)) whether there is a recursively enumerable degree of unsolvability d such that
for all n ≧ 0. Sacks points out that the set of conditions which d must satisfy is not arithmetical. For this reason he suggests that a proof of (Q5) might require some new combinatorial device. The purpose of this note is to show how (Q5) may be proved simply by extending the methods of [l].2
Publisher
Cambridge University Press (CUP)
Cited by
7 articles.
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1. The ω-Turing degrees;Annals of Pure and Applied Logic;2014-09
2. Elementary differences among jump classes;Theoretical Computer Science;2009-03
3. On the ordering of classes in high/low hierarchies;Lecture Notes in Mathematics;1985
4. Pseudojump operators. I. The r.e. case;Transactions of the American Mathematical Society;1983
5. Recursively enumerable sets and degrees;Bulletin of the American Mathematical Society;1978