116b- Lecture 16

By andrescaicedo

(Covered by Todor Tsankov)

We defined the analog K_X of the halting problem for any oracle X and showed that any set r.e. in X is many-to-one reducible to K_X (in particular, it is recursive in K_X). Hence, K_X is a complete \Sigma_1(X) set and no such set is recursive in X.

We proved the S-m-n (or index function) theorem and Kleene’s recursion (or fixed point) theorem. Finally, we introduced the notion of an index set and proved Rice’s theorem that the only recursive index sets are {\mathbb N} and \emptyset.

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