English

Luzin's (N) and randomness reflection

Logic 2020-09-29 v2

Abstract

We show that a computable function f:RRf:\mathbb R\rightarrow\mathbb R has Luzin's property (N) if and only if it reflects Π11\Pi^1_1-randomnes, if and only if it reflects Δ11(O)\Delta^1_1(\mathcal O)-randomness, and if and only if it reflects O\mathcal O-Kurtz randomness, but reflecting Martin-L\"of randomness or weak-2-randomness does not suffice. Here a function ff is said to reflect a randomness notion RR if whenever f(x)f(x) is RR-random, then xx is RR-random as well. If additionally ff is known to have bounded variation, then we show ff has Luzin's (N) if and only if it reflects weak-2-randomness, and if and only if it reflects \emptyset'-Kurtz randomness. This links classical real analysis with algorithmic randomness.

Keywords

Cite

@article{arxiv.2006.07517,
  title  = {Luzin's (N) and randomness reflection},
  author = {Arno Pauly and Linda Westrick and Liang Yu},
  journal= {arXiv preprint arXiv:2006.07517},
  year   = {2020}
}

Comments

25 pages

R2 v1 2026-06-23T16:17:37.121Z