English

Which DNR can be minimal

Logic 2020-06-08 v2

Abstract

Khan and Miller proved that for every computable non decreasing unbounded function hωωh\in \omega^\omega (henceforth order function), if hh is sufficiently large, then there exists a DNRhDNR_h that is of minimal degree. Where hh has to satisfy limnh(n)/(2km<nh(m))=\lim_{n\rightarrow\infty} h(n)/(2^{k\cdot \prod_{m<n}h(m)})=\infty for all k>0k>0. Their core argument is that we can thin the tree by a factor of 2j2^j to make jj Turing functional split. We improve their result by reducing this factor to jj. Thus we show that for every order function hh with limnh(n)/(m<nh(m))k=\lim_{n\rightarrow\infty} h(n)/( \prod_{m<n}h(m))^k=\infty for all k>0k>0, there exists a DNRhDNR_h of minimal degree. We answer a question of Brendle, Brooke-Taylor, Ng and Nies by showing that there exists a GωωG\in \omega^\omega such that GG is weakly meager covering, GG does not compute any Schnorr random real and GG does not Schnorr cover REC.

Cite

@article{arxiv.1912.09053,
  title  = {Which DNR can be minimal},
  author = {Lu Liu},
  journal= {arXiv preprint arXiv:1912.09053},
  year   = {2020}
}

Comments

14 pages. Multiple improvements on writting

R2 v1 2026-06-23T12:50:41.496Z