English

Cone avoiding closed sets

Logic 2016-02-12 v1

Abstract

We prove that for an arbitrary subtree TT of 2<ω2^{<\omega} with each element extendable to a path, a given countable class M\mathcal{M} closed under disjoint union, and any set AA, if none of the members of M\mathcal{M} strongly kk-enumerate TT for any kk, then there exists an infinite set contained in either AA or Aˉ\bar{A} such that for every CMC\in\mathcal{M}, CGC\oplus G also does not strongly kk-enumerate TT. We give applications of this result, which include: (1) RT22\mathsf{RT_2^2} doesn't imply WWKL0\mathsf{WWKL_0}; (2) (Ambos-Spies et al.2004) DNR\mathsf{DNR} is strictly weaker than WWKL0\mathsf{WWKL_0}; (3) (Kjos-Hanssen 2009) for any Martin-L\"{o}f random set AA either AA or Aˉ\bar{A} contains an infinite subset that does not compute any Martin-L\"{o}f random set; etc. We also discuss further generalizations of this result.

Keywords

Cite

@article{arxiv.1602.03777,
  title  = {Cone avoiding closed sets},
  author = {Lu Liu},
  journal= {arXiv preprint arXiv:1602.03777},
  year   = {2016}
}

Comments

22 pages

R2 v1 2026-06-22T12:48:27.354Z