On the cardinality of <em>S</em>(<em>n</em>)-Spaces

Review

On the cardinality of S(n)-Spaces

Published in: Quaestiones Mathematicae
Volume 44 , issue 1 , 2021 , pages: 121–128
DOI: 10.2989/16073606.2019.1672112
Author(s): Alexander V. Osipov , Russia

Abstract

In this paper, for a topological space X and any positive integer n, we define the cardinal functions sLθ (n) (X), θ(n)-quasi-Menger number qM θ(n) (X) and s(n)-quasi-Menger number qM s(n) (X). We prove the following statements:

For every S(2n)-space X, |X| ≤ 2 sL θ (n) (X) κθ ( n ) (X).

For every S(2n)-space X, |X| ≤ 2 qM θ (n) (X) κθ ( n ) (X).

For every S(2n)-space X, |X| ≤ 2 qM s (n) (X) κθ ( n ) (X).

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