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This article is cited in 3 scientific papers (total in 3 papers)
Turing degrees in refinements of the arithmetical hierarchy
V. L. Selivanovab, M. M. Yamaleevb a Ershov Institute of Informatics Systems, pr. Akad. Lavrent'eva 6, Novosibirsk, 630090 Russia
b Kazan (Volga Region) Federal University, ul. Kremlevskaya 18, Kazan, 420008 Russia
Abstract:
We investigate the problem of characterizing proper levels of the fine hierarchy (up to Turing equivalence). It is known that the fine hierarchy exhausts arithmetical sets and contains as a small fragment finite levels of Ershov hierarchies (relativized to $\varnothing^n$, $n<\omega$), which are known to be proper. Our main result is finding a least new (i.e., distinct from the levels of the relativized Ershov hierarchies) proper level. We also show that not all new levels are proper.
Keywords:
Ershov hierarchy, fine hierarchy, arithmetical hierarchy, Turing degrees.
Received: 12.12.2016 Revised: 20.10.2017
Citation:
V. L. Selivanov, M. M. Yamaleev, “Turing degrees in refinements of the arithmetical hierarchy”, Algebra Logika, 57:3 (2018), 338–361; Algebra and Logic, 57:3 (2018), 222–236
Linking options:
https://www.mathnet.ru/eng/al853 https://www.mathnet.ru/eng/al/v57/i3/p338
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Abstract page: | 313 | Full-text PDF : | 49 | References: | 38 | First page: | 10 |
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