Completeness properties in a broader context

We give a characterization of cofinal local compactness for all totally dis- connected cosmic spaces. As an application of this result we prove that an ultrafilter ξ ∈ βω\ωis a P -point in βω\ω if and only if the space ω ∪ {ξ} is cofinally locally compact. We also show that a subspace X of an ordinal is cofinally locally compact if and only if ext(X ) ≤ ω and every closed countable subspace of X is locally compact. It is established that, for any GO space X , if is Čech-complete (metrizable) for any discrete set D ⊂ X × X , then X is Čech-complete (or metrizable respectively). Besides, it is proved that discrete Čech-completeness of a metric space implies its Baire property. Our results provide an answer to a published open question.

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Publication Details

Journal
Quaestiones Mathematicae
Published
2026-07-24
DOI
https://doi.org/10.2989/16073606.2026.2700017
Primary Topic
Advanced Topology and Set Theory
Type
article
Field-Weighted Citation Impact
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article

Completeness properties in a broader context

Vladimir V. Tkachuk, Joel Alberto Aguilar-Velázquez
Quaestiones Mathematicae
Advanced Topology and Set Theory
article

Completeness properties in a broader context

Vladimir V. Tkachuk, Joel Alberto Aguilar-Velázquez
article en

Abstract

We give a characterization of cofinal local compactness for all totally dis- connected cosmic spaces. As an application of this result we prove that an ultrafilter ξ ∈ βω\ωis a P -point in βω\ω if and only if the space ω ∪ {ξ} is cofinally locally compact. We also show that a subspace X of an ordinal is cofinally locally compact if and only if ext(X ) ≤ ω and every closed countable subspace of X is locally compact. It is established that, for any GO space X , if is Čech-complete (metrizable) for any discrete set D ⊂ X × X , then X is Čech-complete (or metrizable respectively). Besides, it is proved that discrete Čech-completeness of a metric space implies its Baire property. Our results provide an answer to a published open question.

Quaestiones Mathematicae
Universidad Autónoma Metropolitana (MX)
Decent work and economic growth
Openalex Percentile: Top 4%
Advanced Topology and Set Theory
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