Cupping and noncupping in the enumeration degrees of ∑20 sets
نویسندگان
چکیده
منابع مشابه
Cupping and noncupping in the enumeration
We prove the following three theorems on the enumeration degrees of Σ2 sets. Theorem A: There exists a nonzero noncuppable Σ 0 2 enumeration degree. Theorem B: Every nonzero ∆2 enumeration degree is cuppable to 0e by an incomplete total enumeration degree. Theorem C: There exists a nonzero low ∆2 enumeration degree with the anticupping property.
متن کاملCupping Classes of Σ0 2 Enumeration Degrees
We prove that no subclass of the Σ 2 enumeration degrees containing the 3-c.e. enumeration degrees can be cupped to 0e by a single Σ 2 enumeration degree.
متن کاملCupping D20 Enumeration Degrees to 0 e '
In this paper we prove that every nonzero ∆2 e-degree is cuppable to 0e by a 1-generic ∆ 0 2 e-degree (so low and nontotal) and that every nonzero ω-c.e. e-degree is cuppable to 0e by an incomplete
متن کاملThe limitations of cupping in the local structure of the enumeration degrees
We prove that a sequence of sets containing representatives of cupping partners for every nonzero ∆2 enumeration degree cannot have a ∆ 0 2 enumeration. We also prove that no subclass of the Σ 2 enumeration degrees containing the nonzero 3-c.e. enumeration degrees can be cupped to 0e by a single incomplete Σ 2 enumeration degree.
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ژورنال
عنوان ژورنال: Annals of Pure and Applied Logic
سال: 1996
ISSN: 0168-0072
DOI: 10.1016/s0168-0072(96)00009-7