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Some variants of the Rothberger property using generalized open sets. (English) Zbl 1538.54080

Summary: We define and study new weak versions of the classical star-Rothberger covering property using \(\alpha\)-open and \(\theta\)-open sets of a topological space. We discuss their relations with some known weak version of the Rothberger property. It is also proved that for an extremally disconnected \(S\)-paracompact-\(T_2\) space the properties: Rothberger, cf. F. Rothberger, Fundam. Math. 30, 50–55 (1938; Zbl 0018.24701)], M. Scheepers [Topology Appl. 69, No. 1, 31–62 (1996; Zbl 0848.54018)], semi-Rothberger, cf. A. Sabah and M. ud D. Khan [Bull. Iran. Math. Soc. 43, No. 6, 1969–1987 (2017; Zbl 1406.54013)], \(\alpha\)-Rothberger, cf. L. D. R. Kočinac [Filomat 33, No. 5, 1485–1493 (2019; Zbl 1499.54107)], \(\theta\)-Rothberger, cf. [loc. cit.] are equivalent. Moreover, for an extremally disconnected space the \(\theta\)-Rothberger property coincides with the almost Rothberger property, cf. M. Scheepers [Proc. Am. Math. Soc. 127, No. 1, 251–257 (1999; Zbl 0910.90287)].

MSC:

54D20 Noncompact covering properties (paracompact, Lindelöf, etc.)
54A10 Several topologies on one set (change of topology, comparison of topologies, lattices of topologies)
54C08 Weak and generalized continuity
54D10 Lower separation axioms (\(T_0\)–\(T_3\), etc.)