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A class of degrees of unsolvability for functions not possessing a fixed point. (Russian) Zbl 0711.03015
The paper is devoted to the study of the class F of degrees of unsolvability of functions f having no fixed points (i.e. such that $$\forall x(W_{f(x)}\neq W_ x)$$. The main result is that there exists a $$\Pi^ 0_ 1$$ class $${\mathcal A}$$ of sets such that F is equal to $$\{$$ dg(A): $$A\in {\mathcal A}\}$$.
Reviewer: R.Murawski
MSC:
 03D30 Other degrees and reducibilities in computability and recursion theory 03D35 Undecidability and degrees of sets of sentences
Keywords:
degrees of unsolvability