Strong Fréchet properties of spaces constructed from squares and AD families

We answer questions of Arhangel'skiĭ using spaces defined from combinatorial objects. We first establish further convergence properties of a space constructed from □ ( κ ) showing it is Fréchet-Urysohn for finite sets and a w-space that is not a W-space. We also show that under additional assum...

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Veröffentlicht in:Applied general topology 2023-10, Vol.24 (2), p.379-389
Hauptverfasser: Chen-Mertens, William, Corral-Rojas, César, Szeptycki, Paul J.
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Sprache:eng
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Zusammenfassung:We answer questions of Arhangel'skiĭ using spaces defined from combinatorial objects. We first establish further convergence properties of a space constructed from □ ( κ ) showing it is Fréchet-Urysohn for finite sets and a w-space that is not a W-space. We also show that under additional assumptions it may be not bi-sequential, and so providing a consistent example of an absolutely Fréchet α1 space that is not bisequential. In addition, if we do not require the space being α1, we can construct a ZFC example of a countable absolutely Fréchet space that is not bisequential from an almost disjoint family of subsets of the natural numbers.
ISSN:1576-9402
1989-4147
DOI:10.4995/agt.2023.18504