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Rendiconti del Circolo Matematico di Palermo (1952 -)
Article . 2000 . Peer-reviewed
License: Springer TDM
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Article . 2000
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Note on hit-and-miss topologies

Authors: Zsilinszky, László;

Note on hit-and-miss topologies

Abstract

The author continues his paper [Rend. Circ. Mat. Palermo, II. Ser. 45, No. 1, 75-83 (1996; Zbl 0907.54010)], concerning hit-and-miss topologies on the set \(\text{Cl}(X)\) of nonempty closed subsets of a topological space \(X\), taking always closed sets to produce the hit-and-miss basic open sets (\(\Delta\)-topologies). Some known results on first and second countability of the hyperspaces [\textit{G. Di Maio} and \textit{L. Holá}, On hit-and-miss topologies, Rend. Accad. Sci. Fis. Mat., Napoli (4) 62, 103-124 (1995) and with \textit{E. Meccariello}, Rostocker Math. Kolloq. 52, 19-32 (1998; Zbl 0937.54009)] are generalized by dropping assertions on separation properties to weakly-\(R_0\), instead of Hausdorffness or \(T_1\). Furthermore, the author proves, that to be a Tikhonov-space, or completely regular (thus uniformizable), or \(T_3\), or regular, or to have the property \(P_{\Delta}\) with \(\Delta\) being an Uryson family, are all equivalent for the hyperspaces -- without additional requirements to the base space (theorem 2.6). Moreover, it is shown (theorem 2.8), that the following are equivalent for the hyperspaces: metrizability, pseudo-metrizability, to be second countable and regular. The general results are applied especially to Vietoris- and Fell-topology. The reviewer explicitly recommends to read the first part [loc. cit] of this very nice study on \(\Delta\)-topologies, too.

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Keywords

Higher separation axioms (completely regular, normal, perfectly or collectionwise normal, etc.), uniformizability, Metric spaces, metrizability, countability, separation axioms, Hyperspaces in general topology, metrizability

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
2
Average
Average
Average
bronze