Left-separating order types

A well ordering ≺ of a topological space X is left-separating if {x′∈X:x′≺x} is closed in X for any x∈X. A space is left-separated if it has a left-separating well-ordering. The left-separating typeordℓ(X) of a left-separated space X is the minimum of the order types of the left-separating well-orde...

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Veröffentlicht in:Topology and its applications 2020-09, Vol.283, p.107338, Article 107338
Hauptverfasser: Soukup, Lajos, Stanley, Adrienne
Format: Artikel
Sprache:eng
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Zusammenfassung:A well ordering ≺ of a topological space X is left-separating if {x′∈X:x′≺x} is closed in X for any x∈X. A space is left-separated if it has a left-separating well-ordering. The left-separating typeordℓ(X) of a left-separated space X is the minimum of the order types of the left-separating well-orderings of X. We prove that(1)if κ is a regular cardinal, then for each ordinal αω, then for each ordinal α
ISSN:0166-8641
1879-3207
DOI:10.1016/j.topol.2020.107338