| Title:
|
On the cardinality of Urysohn spaces and weakly $H$-closed spaces (English) |
| Author:
|
Basile, Fortunata Aurora |
| Author:
|
Carlson, Nathan |
| Language:
|
English |
| Journal:
|
Mathematica Bohemica |
| ISSN:
|
0862-7959 (print) |
| ISSN:
|
2464-7136 (online) |
| Volume:
|
144 |
| Issue:
|
3 |
| Year:
|
2019 |
| Pages:
|
325-336 |
| Summary lang:
|
English |
| . |
| Category:
|
math |
| . |
| Summary:
|
We introduce the cardinal invariant $\theta $-$aL'(X)$, related to $\theta $-$aL(X)$, and show that if $X$ is Urysohn, then $|X|\leq 2^{\theta \text {-}aL'(X)\chi (X)}$. As $\theta $-$aL'(X)\leq aL(X)$, this represents an improvement of the Bella-Cammaroto inequality. \endgraf We also introduce the classes of firmly Urysohn spaces, related to Urysohn spaces, strongly semiregular spaces, related to semiregular spaces, and weakly $H$-closed spaces, related to $H$-closed spaces. (English) |
| Keyword:
|
Urysohn space |
| Keyword:
|
$\theta $-closure |
| Keyword:
|
pseudocharacter |
| Keyword:
|
almost Lindelöf degree |
| Keyword:
|
cardinality |
| Keyword:
|
cardinal invariant |
| MSC:
|
54A25 |
| MSC:
|
54D10 |
| MSC:
|
54D20 |
| idZBL:
|
Zbl 07088854 |
| idMR:
|
MR3985860 |
| DOI:
|
10.21136/MB.2018.0037-18 |
| . |
| Date available:
|
2019-07-24T11:13:04Z |
| Last updated:
|
2020-07-01 |
| Stable URL:
|
http://hdl.handle.net/10338.dmlcz/147777 |
| . |
| Reference:
|
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| Reference:
|
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| Reference:
|
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| Reference:
|
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| Reference:
|
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| Reference:
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| Reference:
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| Reference:
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| Reference:
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| Reference:
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| Reference:
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| Reference:
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| Reference:
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