Pi01 encodability and omniscient reductions
Logic
2019-09-18 v2
Abstract
A set of integers is computably encodable if every infinite set of integers has an infinite subset computing . By a result of Solovay, the computably encodable sets are exactly the hyperarithmetic ones. In this paper, we extend this notion of computable encodability to subsets of the Baire space and we characterize the encodable compact sets as those who admit a non-empty subset. Thanks to this equivalence, we prove that weak weak K\"onig's lemma is not strongly computably reducible to Ramsey's theorem. This answers a question of Hirschfeldt and Jockusch.
Keywords
Cite
@article{arxiv.1603.01086,
title = {Pi01 encodability and omniscient reductions},
author = {Benoit Monin and Ludovic Patey},
journal= {arXiv preprint arXiv:1603.01086},
year = {2019}
}
Comments
9 pages