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
Source: 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.
Type: Article
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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