Abstract.
We show that the Δ0 2 enumeration degrees are dense. We also show that for every nonzero n-c. e. e-degree a, with n≥ 3, one can always find a nonzero 3-c. e. e-degree b such that b < a on the other hand there is a nonzero ωc. e. e-degree which bounds no nonzero n-c. e. e-degree.
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Received: 13 June 2000 / Published online: 3 October 2001
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Arslanov, M., Kalimullin, I. & Sorbi, A. Density results in the Δ20 e-degrees. Arch. Math. Logic 40, 597–614 (2001). https://doi.org/10.1007/s001530100078
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DOI: https://doi.org/10.1007/s001530100078