Degrees of sets having no subsets of higher m- and t t-degree
We consider sets without subsets of higher m- and t t-degree, that we call m-introimmune and t t-introimmune sets respectively. We study how they are distributed in partially ordered degree structures. We show that: each computably enumerable weak truth-table degree contains m-introimmune Π 1 0 -sets; each hyperimmune degree contains bi-m-introimmune sets. Finally, from known results we establish that each degree a with a ′ ⩾ 0 ″ covers a degree containing t t-introimmune sets.
2001 ◽
Vol 107
(1-3)
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pp. 35-48
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2005 ◽
pp. 8-17
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2016 ◽
Vol 28
(3)
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pp. 457-471
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Keyword(s):