English

Infinite dimensional sequential compactness: Sequential compactness based on barriers

General Topology 2023-12-19 v4 Combinatorics Logic

Abstract

We introduce a generalization of sequential compactness using barriers on ω\omega extending naturally the notion introduced in [W. Kubi\'{s} and P. Szeptycki, On a topological Ramsey theorem, \emph{Canad. Math. Bull.}, 66 (2023), {156}--{165}]. We improve results from [C. Corral and O. Guzm{\'a}n and C. L{\'o}pez-Callejas, High dimensional sequential compactness, \emph{Fund. Math.}] by building spaces that are B\mathcal{B}-sequentially compact but no C\mathcal{C}-sequentially compact when the barriers B\mathcal{B} and C\mathcal{C} satisfy certain rank assumption which turns out to be equivalent to a Kat\v{e}tov-order assumption. Such examples are constructed under the assumption b=c\mathfrak{b} =\mathfrak{c}. We also exhibit some classes of spaces that are B\mathcal{B}-sequentially compact for every barrier B\mathcal{B}, including some classical classes of compact spaces from functional analysis, and as a byproduct we obtain some results on angelic spaces. Finally we introduce and compute some cardinal invariants naturally associated to barriers.

Keywords

Cite

@article{arxiv.2309.04397,
  title  = {Infinite dimensional sequential compactness: Sequential compactness based on barriers},
  author = {Cesar Corral and Osvaldo Guzman and Carlos Lopez-Callejas and Pourya Memarpanahi and Paul Szeptycki and Stevo Todorcevic},
  journal= {arXiv preprint arXiv:2309.04397},
  year   = {2023}
}