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Remarks on new star-selection principles in topology.
- Source :
-
Topology & Its Applications . Dec2019, Vol. 268, pN.PAG-N.PAG. 1p. - Publication Year :
- 2019
-
Abstract
- In this paper, we study some new selection principles using the star operator which was introduced by Bal and Bhowmik (2017) [1]. We first prove that there exists a space X which has the property U f i n ⁎ (O , O) but does not have the property U f i n ⁎ (O , O) , where O denotes the collection of all open covers of a space X. We also obtain several examples of spaces having the property U 1 ⁎ (O , O) but their products do not have the property U 1 ⁎ (O , O). A Tychonoff example of a space having the property U 1 ⁎ (O , O) which is not star countable is also given. If a space X has the property U 1 ⁎ (O , O) (respectively, U f i n ⁎ (O , O)) and e (X) < ω 1 , then the Alexandroff duplicate A (X) has the property U 1 ⁎ (O , O) (respectively, U f i n ⁎ (O , O)). Finally, we prove that the property U 1 ⁎ (O , O) is not hereditary with respect to regular closed subsets and every regular paraLindelöf 1-star-Lindelöf space is Lindelöf. The above-mentioned results answer two published open questions from [1]. [ABSTRACT FROM AUTHOR]
- Subjects :
- *TOPOLOGY
*OPEN spaces
*OPEN-ended questions
Subjects
Details
- Language :
- English
- ISSN :
- 01668641
- Volume :
- 268
- Database :
- Academic Search Index
- Journal :
- Topology & Its Applications
- Publication Type :
- Academic Journal
- Accession number :
- 139407149
- Full Text :
- https://doi.org/10.1016/j.topol.2019.106921