English

On the interplay between effective notions of randomness and genericity

Logic 2019-03-27 v1

Abstract

In this paper, we study the power and limitations of computing effectively generic sequences using effectively random oracles. Previously, it was known that every 2-random sequence computes a 1-generic sequence (as shown by Kautz) and every 2-random sequence forms a minimal pair in the Turing degrees with every 2-generic sequence (as shown by Nies, Stephan, and Terwijn). We strengthen these results by showing that every Demuth random sequence computes a 1-generic sequence (which answers an open question posed by Barmpalias, Day, and Lewis) and that every Demuth random sequence forms a minimal pair with every pb-generic sequence (where pb-genericity is an effective notion of genericity that is strictly between 1-genericity and 2-genericity). Moreover, we prove that for every comeager G2ω\mathcal{G}\subseteq 2^\omega, there is some weakly 2-random sequence XX that computes some YGY\in\mathcal{G}, a result that allows us to provide a fairly complete classification as to how various notions of effective randomness interact in the Turing degrees with various notions of effective genericity.

Keywords

Cite

@article{arxiv.1804.09774,
  title  = {On the interplay between effective notions of randomness and genericity},
  author = {Laurent Bienvenu and Christopher P. Porter},
  journal= {arXiv preprint arXiv:1804.09774},
  year   = {2019}
}