English

Concentrated sets and the Hurewicz property

General Topology 2025-11-13 v1

Abstract

A set of reals XX is b\mathfrak{b}-concentrated if it has cardinality at least b\mathfrak{b} and it contains a countable set DXD\subseteq X such that each closed subset of XX disjoint with DD has size smaller than b\mathfrak{b}. We present ZFC results about structures of b\mathfrak{b}-concentrated sets with the Hurewicz covering property using semifilters. Then we show that assuming that the semifilter trichotomy holds, then each b\mathfrak{b}-concentrated set is Hurewicz and even productively Hurewicz. We also show that the appearance of Hurewicz b\mathfrak{b}-concentrated sets under the semifilter trichotomy is somewhat specific and the situation in the Laver model for the consitency of the Borel Conjecture is different.

Keywords

Cite

@article{arxiv.2511.09320,
  title  = {Concentrated sets and the Hurewicz property},
  author = {Valentin Haberl and Piotr Szewczak and Lyubomyr Zdomskyy},
  journal= {arXiv preprint arXiv:2511.09320},
  year   = {2025}
}

Comments

20 p