属于D空间的Box和nabla产品

IF 0.5 4区 数学 Q3 MATHEMATICS
H.A. Barriga-Acosta , P.M. Gartside
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The box product, <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span>, is <span><math><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></math></span> with topology generated by all <span><math><mrow><msub><mrow><mo>∏</mo></mrow><mrow><mi>n</mi></mrow></msub><msub><mrow><mi>U</mi></mrow><mrow><mi>n</mi></mrow></msub></mrow></math></span>, where every <span><math><msub><mrow><mi>U</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> is open. The nabla product, <span><math><mrow><mo>∇</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span>, is obtained from <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> by quotienting out mod-finite. The weight of <span><math><mi>X</mi></math></span>, <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow></mrow></math></span>, is the minimal size of a base, while <span><math><mrow><mi>d</mi><mo>=</mo><mo>cof</mo><msup><mrow><mi>ω</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span>.</p><p>It is shown that there are specific compact spaces <span><math><mi>X</mi></math></span> such that <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> and <span><math><mrow><mo>∇</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> are not <span><math><mi>D</mi></math></span>, but in general:</p><p>(1) <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> and <span><math><mrow><mo>∇</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> are hereditarily <span><math><mi>D</mi></math></span> if <span><math><mi>X</mi></math></span> is scattered and either hereditarily paracompact or of finite scattered height, or if <span><math><mi>X</mi></math></span> is metrizable (and <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow><mo>≤</mo><mi>d</mi></mrow></math></span> for <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span>);</p><p>(2) <span><math><mrow><mo>∇</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> is hereditarily <span><math><mi>D</mi></math></span> if <span><math><mi>X</mi></math></span> is first countable and <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow><mo>≤</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></math></span>, or <em>consistently</em> if <span><math><mi>X</mi></math></span> is first countable and <span><math><mrow><mo>|</mo><mi>X</mi><mo>|</mo><mo>≤</mo><mi>c</mi></mrow></math></span>, or <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow><mo>≤</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></math></span>; and</p><p>(3) <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> is <span><math><mi>D</mi></math></span> <em>consistently</em> if <span><math><mi>X</mi></math></span> is compact and either first countable or <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow><mo>≤</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></math></span>.</p></div>","PeriodicalId":56126,"journal":{"name":"Indagationes Mathematicae-New Series","volume":null,"pages":null},"PeriodicalIF":0.5000,"publicationDate":"2023-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Box and nabla products that are D-spaces\",\"authors\":\"H.A. 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The box product, <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span>, is <span><math><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></math></span> with topology generated by all <span><math><mrow><msub><mrow><mo>∏</mo></mrow><mrow><mi>n</mi></mrow></msub><msub><mrow><mi>U</mi></mrow><mrow><mi>n</mi></mrow></msub></mrow></math></span>, where every <span><math><msub><mrow><mi>U</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> is open. The nabla product, <span><math><mrow><mo>∇</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span>, is obtained from <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> by quotienting out mod-finite. The weight of <span><math><mi>X</mi></math></span>, <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow></mrow></math></span>, is the minimal size of a base, while <span><math><mrow><mi>d</mi><mo>=</mo><mo>cof</mo><msup><mrow><mi>ω</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span>.</p><p>It is shown that there are specific compact spaces <span><math><mi>X</mi></math></span> such that <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> and <span><math><mrow><mo>∇</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> are not <span><math><mi>D</mi></math></span>, but in general:</p><p>(1) <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> and <span><math><mrow><mo>∇</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> are hereditarily <span><math><mi>D</mi></math></span> if <span><math><mi>X</mi></math></span> is scattered and either hereditarily paracompact or of finite scattered height, or if <span><math><mi>X</mi></math></span> is metrizable (and <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow><mo>≤</mo><mi>d</mi></mrow></math></span> for <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span>);</p><p>(2) <span><math><mrow><mo>∇</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> is hereditarily <span><math><mi>D</mi></math></span> if <span><math><mi>X</mi></math></span> is first countable and <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow><mo>≤</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></math></span>, or <em>consistently</em> if <span><math><mi>X</mi></math></span> is first countable and <span><math><mrow><mo>|</mo><mi>X</mi><mo>|</mo><mo>≤</mo><mi>c</mi></mrow></math></span>, or <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow><mo>≤</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></math></span>; and</p><p>(3) <span><math><mrow><mo>□</mo><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></mrow></math></span> is <span><math><mi>D</mi></math></span> <em>consistently</em> if <span><math><mi>X</mi></math></span> is compact and either first countable or <span><math><mrow><mi>w</mi><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow><mo>≤</mo><msub><mrow><mi>ω</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></math></span>.</p></div>\",\"PeriodicalId\":56126,\"journal\":{\"name\":\"Indagationes Mathematicae-New Series\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.5000,\"publicationDate\":\"2023-05-03\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Indagationes Mathematicae-New Series\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0019357723000381\",\"RegionNum\":4,\"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":"Indagationes Mathematicae-New Series","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0019357723000381","RegionNum":4,"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

空间X是D,如果对于X中每个点X的开邻域的每一个赋值U,都有一个闭的离散D,使得⋃{U(X):X∈D}=X。盒子产品,□Xω,是拓扑由所有πnUn生成的Xω,其中每个Un是开的。nabla乘积,ŞXω,由□Xω的模有限商。X的权重w(X)是基的最小大小,而d=cofω。证明了存在特定的紧致空间X,使得□Xω和ŞXω不是D,但一般来说:(1)□如果X是散射的并且是可遗传的仿紧的或者是有限散射高度的,或者如果X是可度量的(并且w(X)≤D□Xω);(2) 如果X是第一可数且w(X)≤ω1,或一致地如果X是一可数且|X|≤c,或w(X;和(3)□如果X是紧致的并且是第一可数的或者w(X)≤ω1,则Xω一致为D。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Box and nabla products that are D-spaces

A space X is D if for every assignment, U, of an open neighborhood to each point x in X there is a closed discrete D such that {U(x):xD}=X. The box product, Xω, is Xω with topology generated by all nUn, where every Un is open. The nabla product, Xω, is obtained from Xω by quotienting out mod-finite. The weight of X, w(X), is the minimal size of a base, while d=cofωω.

It is shown that there are specific compact spaces X such that Xω and Xω are not D, but in general:

(1) Xω and Xω are hereditarily D if X is scattered and either hereditarily paracompact or of finite scattered height, or if X is metrizable (and w(X)d for Xω);

(2) Xω is hereditarily D if X is first countable and w(X)ω1, or consistently if X is first countable and |X|c, or w(X)ω1; and

(3) Xω is D consistently if X is compact and either first countable or w(X)ω1.

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来源期刊
CiteScore
1.20
自引率
16.70%
发文量
74
审稿时长
79 days
期刊介绍: Indagationes Mathematicae is a peer-reviewed international journal for the Mathematical Sciences of the Royal Dutch Mathematical Society. The journal aims at the publication of original mathematical research papers of high quality and of interest to a large segment of the mathematics community. The journal also welcomes the submission of review papers of high quality.
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