Classifying C.E. Sets
In §1.6 we constructed a noncomputable c.e. set K. In §2.4 we studied creative sets and showed that all are computably isomorphic to K. So far the noncomputable c.e. sets we have exhibited are all computably isomorphic to K and therefore of Turing degree 0′. Post in [Post 1944] asked whether there is only one noncomputable c.e. set up to Turing equivalence.
KeywordsComputable Function Computable Enumeration Turing Degree Nonzero Degree Turing Reduction
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