English

New Hindman spaces

General Topology 2023-08-29 v1 Combinatorics Logic

Abstract

We introduce a method that allows to turn topological questions about Hindman spaces into purely combinatorial questions about the Kat\v{e}tov order of ideals on N\mathbb{N}. We also provide two applications of the method. (1) We characterize FσF_\sigma ideals I\mathcal{I} for which there is a Hindman space which is not an I\mathcal{I}-space under the continuum hypothesis. This reduces a topological question of Albin L. Jones about consistency of existence of a Hindman space which is not van der Waerden to the question whether the ideal of all non AP-sets is not below the ideal of all non IP-sets in the Kat\v{e}tov order. (2) Under the continuum hypothesis, we construct a Hindman space which is not an I1/n\mathcal{I}_{1/n}-space. This answers a question posed by Jana Fla\v{s}kov\'{a} at the 22nd Summer Conference on Topology and its Applications.

Keywords

Cite

@article{arxiv.2308.14396,
  title  = {New Hindman spaces},
  author = {Rafał Filipów and Krzysztof Kowitz and Adam Kwela and Jacek Tryba},
  journal= {arXiv preprint arXiv:2308.14396},
  year   = {2023}
}
R2 v1 2026-06-28T12:05:49.868Z