| Title:
|
$\omega$H-sets and cardinal invariants (English) |
| Author:
|
Fedeli, Alessandro |
| Language:
|
English |
| Journal:
|
Commentationes Mathematicae Universitatis Carolinae |
| ISSN:
|
0010-2628 (print) |
| ISSN:
|
1213-7243 (online) |
| Volume:
|
39 |
| Issue:
|
2 |
| Year:
|
1998 |
| Pages:
|
367-370 |
| . |
| Category:
|
math |
| . |
| Summary:
|
A subset $A$ of a Hausdorff space $X$ is called an $\omega$H-set in $X$ if for every open family $\Cal U$ in $X$ such that $A \subset \bigcup \Cal U$ there exists a countable subfamily $\Cal V$ of $\Cal U$ such that $A \subset \bigcup \{ \overline{V} : V \in \Cal V \}$. In this paper we introduce a new cardinal function $t_{s\theta}$ and show that $|A| \leq 2^{t_{s\theta}(X)\psi_{c}(X)}$ for every $\omega$H-set $A$ of a Hausdorff space $X$. (English) |
| Keyword:
|
cardinal function |
| Keyword:
|
$\omega$H-set |
| MSC:
|
54A25 |
| MSC:
|
54D20 |
| idZBL:
|
Zbl 0937.54004 |
| idMR:
|
MR1651975 |
| . |
| Date available:
|
2009-01-08T18:41:08Z |
| Last updated:
|
2012-04-30 |
| Stable URL:
|
http://hdl.handle.net/10338.dmlcz/119013 |
| . |
| Reference:
|
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| Reference:
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| . |
