A Δ20 set with no infinite low subset in either it or its complement
- 1 September 2001
- journal article
- Published by Cambridge University Press (CUP) in The Journal of Symbolic Logic
- Vol. 66 (3), 1371-1381
- https://doi.org/10.2307/2695113
Abstract
We construct the set of the title, answering a question of Cholak, Jockusch. and Slaman [1], and discuss its connections with the study of the proof-theoretic strength and effective content of versions of Ramsey's Theorem. In particular, our result implies that every ω-model of must contain a nonlow set.Keywords
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