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On universal pairs in the Ershov hierarchy
N. A. Bazhenovab, M. Mustafac, S. S. Ospichevab a Sobolev Institute of Mathematics,
Novosibirsk, Russia
b Novosibirsk State University, Novosibirsk, Russia
c Nazarbayev University, Nur-Sultan, Kazakhstan
Abstract:
We develop the Ershov theory of $C$-classes for some finite families of sets in the Ershov hierarchy. We generalize the result by Muchnik on multiple $m$-reducibility as follows: There exists an $m$-universal pair of disjoint sets for each level of the Ershov hierarchy.
Keywords:
Ershov hierarchy, $m$-reducibility, $C$-class, computable numbering.
Received: 07.05.2020 Revised: 18.09.2020 Accepted: 09.10.2020
Citation:
N. A. Bazhenov, M. Mustafa, S. S. Ospichev, “On universal pairs in the Ershov hierarchy”, Sibirsk. Mat. Zh., 62:1 (2021), 31–41; Siberian Math. J., 62:1 (2021), 23–31
Linking options:
https://www.mathnet.ru/eng/smj7535 https://www.mathnet.ru/eng/smj/v62/i1/p31
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