{"title":"关于元素具有 H 封闭闭合的$$/pi$$-基空间","authors":"D. Giacopello","doi":"10.1007/s10474-024-01450-x","DOIUrl":null,"url":null,"abstract":"<div><p>We deal with the class of Hausdorff spaces having a <span>\\(\\pi\\)</span>-base whose elements have an H-closed closure. Carlson proved that <span>\\(|X|\\leq 2^{wL(X)\\psi_c(X)t(X)}\\)</span> for every quasiregular space <span>\\(X\\)</span> with a <span>\\(\\pi\\)</span>-base whose elements have an H-closed closure. We provide an example of a space <span>\\(X\\)</span> having a <span>\\(\\pi\\)</span>-base whose elements have an H-closed closure which is not quasiregular (neither Urysohn) such that <span>\\(|X|> 2^{wL(X)\\chi(X)}\\)</span> (then <span>\\(|X|> 2^{wL(X)\\psi_c(X)t(X)}\\)</span>). Always in the class of spaces with a <span>\\(\\pi\\)</span>-base whose elements have an H-closed closure, we establish the bound <span>\\(|X|\\leq2^{wL(X)k(X)}\\)</span> for Urysohn spaces and we give an example of an Urysohn space <span>\\(Z\\)</span> such that <span>\\(k(Z)<\\chi(Z)\\)</span>. Lastly, we present some equivalent conditions to the Martin's Axiom involving spaces with a <span>\\(\\pi\\)</span>-base whose elements have an H-closed closure and, additionally, we prove that if a quasiregular space has a <span>\\(\\pi\\)</span>-base whose elements have an H-closed closure then such a space is Baire.</p></div>","PeriodicalId":50894,"journal":{"name":"Acta Mathematica Hungarica","volume":"173 2","pages":"448 - 460"},"PeriodicalIF":0.6000,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"On spaces with a \\\\(\\\\pi\\\\)-base whose elements have an H-closed closure\",\"authors\":\"D. Giacopello\",\"doi\":\"10.1007/s10474-024-01450-x\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>We deal with the class of Hausdorff spaces having a <span>\\\\(\\\\pi\\\\)</span>-base whose elements have an H-closed closure. Carlson proved that <span>\\\\(|X|\\\\leq 2^{wL(X)\\\\psi_c(X)t(X)}\\\\)</span> for every quasiregular space <span>\\\\(X\\\\)</span> with a <span>\\\\(\\\\pi\\\\)</span>-base whose elements have an H-closed closure. We provide an example of a space <span>\\\\(X\\\\)</span> having a <span>\\\\(\\\\pi\\\\)</span>-base whose elements have an H-closed closure which is not quasiregular (neither Urysohn) such that <span>\\\\(|X|> 2^{wL(X)\\\\chi(X)}\\\\)</span> (then <span>\\\\(|X|> 2^{wL(X)\\\\psi_c(X)t(X)}\\\\)</span>). Always in the class of spaces with a <span>\\\\(\\\\pi\\\\)</span>-base whose elements have an H-closed closure, we establish the bound <span>\\\\(|X|\\\\leq2^{wL(X)k(X)}\\\\)</span> for Urysohn spaces and we give an example of an Urysohn space <span>\\\\(Z\\\\)</span> such that <span>\\\\(k(Z)<\\\\chi(Z)\\\\)</span>. Lastly, we present some equivalent conditions to the Martin's Axiom involving spaces with a <span>\\\\(\\\\pi\\\\)</span>-base whose elements have an H-closed closure and, additionally, we prove that if a quasiregular space has a <span>\\\\(\\\\pi\\\\)</span>-base whose elements have an H-closed closure then such a space is Baire.</p></div>\",\"PeriodicalId\":50894,\"journal\":{\"name\":\"Acta Mathematica Hungarica\",\"volume\":\"173 2\",\"pages\":\"448 - 460\"},\"PeriodicalIF\":0.6000,\"publicationDate\":\"2024-08-22\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Acta Mathematica Hungarica\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s10474-024-01450-x\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Acta Mathematica Hungarica","FirstCategoryId":"100","ListUrlMain":"https://link.springer.com/article/10.1007/s10474-024-01450-x","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
摘要
我们要讨论的是一类具有其元素具有 H 闭合的 \(\pi\)-base 的 Hausdorff 空间。卡尔森(Carlson)证明了对于每一个具有其元素有一个 H 封闭闭合的基的准线性空间 \(X\) 来说,\(|X|leq 2^{wL(X)\psi_c(X)t(X)}\) 是一个具有 H 封闭闭合的基的准线性空间。我们举例说明了一个有一个其元素有一个 H 封闭闭包的空间 \(X\),它不是类线性的(既不是 Urysohn),这样 \(|X|> 2^{wL(X)\chi(X)}\) (然后 \(|X|>2^{wL(X)\psi_c(X)t(X)}/))。总是在元素具有 H 闭合的、具有 \(\pi\)-base 的空间类别中,我们为 Urysohn 空间建立了约束 \(|X|\leq2^{wL(X)k(X)}\),并给出了一个 Urysohn 空间 \(Z\) 的例子,使得 \(k(Z)<\chi(Z)\)。最后,我们提出了马丁公理(Martin's Axiom)的一些等价条件,这些条件涉及到具有其元素具有 H 封闭闭合的 \(\pi\)-base 的空间,此外,我们还证明了如果一个准线性空间具有其元素具有 H 封闭闭合的 \(\pi\)-base ,那么这样的空间就是拜尔空间。
On spaces with a \(\pi\)-base whose elements have an H-closed closure
We deal with the class of Hausdorff spaces having a \(\pi\)-base whose elements have an H-closed closure. Carlson proved that \(|X|\leq 2^{wL(X)\psi_c(X)t(X)}\) for every quasiregular space \(X\) with a \(\pi\)-base whose elements have an H-closed closure. We provide an example of a space \(X\) having a \(\pi\)-base whose elements have an H-closed closure which is not quasiregular (neither Urysohn) such that \(|X|> 2^{wL(X)\chi(X)}\) (then \(|X|> 2^{wL(X)\psi_c(X)t(X)}\)). Always in the class of spaces with a \(\pi\)-base whose elements have an H-closed closure, we establish the bound \(|X|\leq2^{wL(X)k(X)}\) for Urysohn spaces and we give an example of an Urysohn space \(Z\) such that \(k(Z)<\chi(Z)\). Lastly, we present some equivalent conditions to the Martin's Axiom involving spaces with a \(\pi\)-base whose elements have an H-closed closure and, additionally, we prove that if a quasiregular space has a \(\pi\)-base whose elements have an H-closed closure then such a space is Baire.
期刊介绍:
Acta Mathematica Hungarica is devoted to publishing research articles of top quality in all areas of pure and applied mathematics as well as in theoretical computer science. The journal is published yearly in three volumes (two issues per volume, in total 6 issues) in both print and electronic formats. Acta Mathematica Hungarica (formerly Acta Mathematica Academiae Scientiarum Hungaricae) was founded in 1950 by the Hungarian Academy of Sciences.