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On properties related to star countability.

Authors :
Xuan, Wei-Feng
Song, Yan-Kui
Source :
Topology & Its Applications. Sep2018, Vol. 247, p20-28. 9p.
Publication Year :
2018

Abstract

We prove that a Hausdorff metaLindelöf weakly star countable space is feebly Lindelöf and a Hausdorff metacompact weakly star finite space is almost compact which partially answers a question of Alas and Wilson (2017) [2, Question 3.14] . We also obtain a normal example of a weakly star countable space which is neither almost star countable nor star Lindelöf without any set-theoretic assumptions, which answers a question implicitly asked by Song (2015) [13, Remark 2.8] and a question asked by Alas, Junqueira and Wilson (2011) [3, Question 4] . Under MA+¬CH, there even exists a normal weakly star countable Moore space which is not almost star countable. An example of a Tychonoff star compact and weakly star finite space which is not star countable is also given. Finally, we prove that every weakly star countable Hausdorff space with a rank 4-diagonal has cardinality at most 2 ω . [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
01668641
Volume :
247
Database :
Academic Search Index
Journal :
Topology & Its Applications
Publication Type :
Academic Journal
Accession number :
131402804
Full Text :
https://doi.org/10.1016/j.topol.2018.07.009