English

Topological complexity of ideal limit points

General Topology 2024-07-18 v1 Classical Analysis and ODEs Functional Analysis

Abstract

Given an ideal I\mathcal{I} on the nonnegative integers ω\omega and a Polish space XX, let L(I)\mathscr{L}(\mathcal{I}) be the family of subsets SXS\subseteq X such that SS is the set of I\mathcal{I}-limit points of some sequence taking values in XX. First, we show that L(I)\mathscr{L}(\mathcal{I}) may attain arbitrarily large Borel complexity. Second, we prove that if I\mathcal{I} is a GδσG_{\delta\sigma}-ideal then all elements of L(I)\mathscr{L}(\mathcal{I}) are closed. Third, we show that if I\mathcal{I} is a simply coanalytic ideal and XX is first countable, then every element of L(I)\mathscr{L}(\mathcal{I}) is simply analytic. Lastly, we studied certain structural properties and the topological complexity of minimal ideals I\mathcal{I} for which L(I)\mathscr{L}(\mathcal{I}) contains a given set.

Keywords

Cite

@article{arxiv.2407.12160,
  title  = {Topological complexity of ideal limit points},
  author = {Marek Balcerzak and Szymon Glab and Paolo Leonetti},
  journal= {arXiv preprint arXiv:2407.12160},
  year   = {2024}
}
R2 v1 2026-06-28T17:43:47.307Z