English

Meager-additive sets in topological groups

General Topology 2018-06-19 v1 Functional Analysis Metric Geometry

Abstract

By the Galvin-Mycielski-Solovay theorem, a subset XX of the line has Borel's strong measure zero if and only if M+XRM+X\neq\mathbb{R} for each meager set MM. A set XRX\subseteq\mathbb{R} is meager-additive if M+XM+X is meager for each meager set MM. Recently a theorem on meager-additive sets that perfectly parallels the Galvin-Mycielski-Solovay theorem was proven: A set XRX\subseteq\mathbb{R} is meager-additive if and only if it has sharp measure zero, a notion akin to strong measure zero. We investigate the validity of this result in Polish groups. We prove, e.g., that a set in a locally compact Polish group admitting an invariant metric is meager-additive if and only if it has sharp measure zero. We derive some consequences and calculate some cardinal invariants.

Keywords

Cite

@article{arxiv.1806.06674,
  title  = {Meager-additive sets in topological groups},
  author = {Ondrej Zindulka},
  journal= {arXiv preprint arXiv:1806.06674},
  year   = {2018}
}
R2 v1 2026-06-23T02:33:11.549Z