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On a Conjecture of Kleene and Post |
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| Authors: | S. Barry Cooper |
| Abstract: | A proof is given that 0 ′ (the argest Turing degree containing a computably enumerable set) is definable in the structure of the degrees of unsolvability. This answers a long‐standing question of Kleene and Post, and has a number of corollaries including the definability of the jump operator. |
| Keywords: | Computably enumerable set Computably enumerable degree Turing degree Jump operator Turing definable |