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Please use this identifier to cite or link to this item: http://hdl.handle.net/10077/4831

Title: Some consequences of an easy cardinal inequality involving separating open covers
Authors: Bella, Angelo
Issue Date: 1989
Publisher: Università degli Studi di Trieste. Dipartimento di Scienze Matematiche
Citation: Angelo Bella, “Some consequences of an easy cardinal inequality involving separating open covers”, in: Rendiconti dell’Istituto di Matematica dell’Università di Trieste. An International Journal of Mathematics, 21 (1989), pp. 1-5.
Series/Report no.: Rendiconti dell’Istituto di Matematica dell’Università di Trieste. An International Journal of Mathematics
21 (1989)
Abstract: Vengono fornite alcune disuguaglianze cardinali relative a varie funzioni cardinali definite in termini di certi ricoprimenti aperti. Tra l'altro si prova che $\mid X\mid\leq e(X)^{\psi m(X)}$ e $\mid X\mid\leq wL(X)^{\psi u(X)}$ per ogni T$_{1}$-spazio x completamente regolare. Qui e (X), wL(X), $\psi m(X)$ e $\psi u(X)$ denotano rispettivamente l'estensione, il numero debole di Lindel$\ddot{\textrm{o}}$f.
Some cardinal inequalities with cardinal functions defined in terms of certain typed of covers are given. Among other results it is shown that $\mid X\mid\leq e(X)^{\psi m(X)}$ and $\mid X\mid\leq wL(X)^{\psi u(X)}$ for any completely regular T$_{1}$-space x. Here e (X), wL(X), $\psi m(X)$ e $\psi u(X)$ denote respectively the extent, the weak Lindel$\ddot{\textrm{o}}$f number, the pseudo-metrizability degree and the pseudo uniform weight of X.
URI: http://hdl.handle.net/10077/4831
ISSN: 0049-4704
Appears in Collections:Rendiconti dell‘ Istituto di matematica dell‘ Università di Trieste: an International Journal of Mathematics vol.21 (1989)

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