English

Goldstern's principle about unions of null sets

Logic 2026-01-27 v4

Abstract

Goldstern showed in his 1993 paper that the union of a real-parametrized, monotone family of Lebesgue measure zero sets has also Lebesgue measure zero provided that the sets are uniformly Σ11\boldsymbol{\Sigma}^1_1. Our aim is to study to what extent we can drop the Σ11\boldsymbol{\Sigma}^1_1 assumption. We show Goldstern's principle for the pointclass Π11\boldsymbol{\Pi}^1_1 holds. We show that Goldstern's principle for the pointclass of all subsets is consistent with ZFC\mathsf{ZFC} and show its negation follows from CH\mathsf{CH}. Also we prove that Goldstern's principle for the pointclass of all subsets holds both under ZF+AD\mathsf{ZF} + \mathsf{AD} and in Solovay models.

Keywords

Cite

@article{arxiv.2206.08147,
  title  = {Goldstern's principle about unions of null sets},
  author = {Tatsuya Goto},
  journal= {arXiv preprint arXiv:2206.08147},
  year   = {2026}
}