{"title":"关于性质 (A) ((σ-A)) 在点上的一些应用","authors":"Liang-Xue Peng","doi":"10.1016/j.topol.2024.109023","DOIUrl":null,"url":null,"abstract":"<div><p>If <em>X</em> is a hereditarily metacompact <em>ω</em>-scattered space and <em>X</em> has a <em>σ</em>-<em>NSR</em> pair-base at every point of <em>X</em>, then <em>X</em> has a <em>σ</em>-<em>NSR</em> pair-base. If <em>X</em> is a hereditarily meta-Lindelöf <em>ω</em>-scattered space and <em>X</em> has a <em>σ</em>-<em>NSR</em> pair-base at every point of <em>X</em>, then <em>X</em> has property (<em>σ</em>-A). If <em>X</em> is a hereditarily meta-Lindelöf GO-space such that every condensation set of <em>X</em> has property (<em>σ</em>-A), then <em>X</em> has property (<em>σ</em>-A). We point out that there is a gap in the proof of Lemma 37 in <span><span>[18]</span></span>. We give a detailed proof for the result. We finally show that if <span><math><mo>(</mo><mi>X</mi><mo>,</mo><mi>τ</mi><mo>,</mo><mo><</mo><mo>)</mo></math></span> is a GO-space and <span><math><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></msup></math></span> has property (A) for some <span><math><mi>n</mi><mo>∈</mo><mi>N</mi></math></span>, then <em>X</em> has property (A), where <span><math><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mn>0</mn><mo>)</mo></mrow></msup><mo>=</mo><mi>X</mi></math></span>, <span><math><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mi>i</mi><mo>+</mo><mn>1</mn><mo>)</mo></mrow></msup><mo>=</mo><mo>{</mo><mi>x</mi><mo>∈</mo><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mi>i</mi><mo>)</mo></mrow></msup><mo>:</mo><mi>x</mi></math></span> is not an isolated point of <span><math><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mi>i</mi><mo>)</mo></mrow></msup><mo>}</mo></math></span> for each <span><math><mi>i</mi><mo><</mo><mi>n</mi></math></span>. If <em>X</em> is a hereditarily meta-Lindelöf <em>ω</em>-scattered GO-space, then <em>X</em> has a <em>σ</em>-<em>NSR</em> pair-base and <span><math><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></math></span> is hereditarily a <em>D</em>-space.</p></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"355 ","pages":"Article 109023"},"PeriodicalIF":0.6000,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"On some applications of property (A) ((σ-A)) at a point\",\"authors\":\"Liang-Xue Peng\",\"doi\":\"10.1016/j.topol.2024.109023\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>If <em>X</em> is a hereditarily metacompact <em>ω</em>-scattered space and <em>X</em> has a <em>σ</em>-<em>NSR</em> pair-base at every point of <em>X</em>, then <em>X</em> has a <em>σ</em>-<em>NSR</em> pair-base. If <em>X</em> is a hereditarily meta-Lindelöf <em>ω</em>-scattered space and <em>X</em> has a <em>σ</em>-<em>NSR</em> pair-base at every point of <em>X</em>, then <em>X</em> has property (<em>σ</em>-A). If <em>X</em> is a hereditarily meta-Lindelöf GO-space such that every condensation set of <em>X</em> has property (<em>σ</em>-A), then <em>X</em> has property (<em>σ</em>-A). We point out that there is a gap in the proof of Lemma 37 in <span><span>[18]</span></span>. We give a detailed proof for the result. We finally show that if <span><math><mo>(</mo><mi>X</mi><mo>,</mo><mi>τ</mi><mo>,</mo><mo><</mo><mo>)</mo></math></span> is a GO-space and <span><math><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></msup></math></span> has property (A) for some <span><math><mi>n</mi><mo>∈</mo><mi>N</mi></math></span>, then <em>X</em> has property (A), where <span><math><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mn>0</mn><mo>)</mo></mrow></msup><mo>=</mo><mi>X</mi></math></span>, <span><math><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mi>i</mi><mo>+</mo><mn>1</mn><mo>)</mo></mrow></msup><mo>=</mo><mo>{</mo><mi>x</mi><mo>∈</mo><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mi>i</mi><mo>)</mo></mrow></msup><mo>:</mo><mi>x</mi></math></span> is not an isolated point of <span><math><msup><mrow><mi>X</mi></mrow><mrow><mo>(</mo><mi>i</mi><mo>)</mo></mrow></msup><mo>}</mo></math></span> for each <span><math><mi>i</mi><mo><</mo><mi>n</mi></math></span>. If <em>X</em> is a hereditarily meta-Lindelöf <em>ω</em>-scattered GO-space, then <em>X</em> has a <em>σ</em>-<em>NSR</em> pair-base and <span><math><msup><mrow><mi>X</mi></mrow><mrow><mi>ω</mi></mrow></msup></math></span> is hereditarily a <em>D</em>-space.</p></div>\",\"PeriodicalId\":51201,\"journal\":{\"name\":\"Topology and its Applications\",\"volume\":\"355 \",\"pages\":\"Article 109023\"},\"PeriodicalIF\":0.6000,\"publicationDate\":\"2024-07-18\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Topology and its Applications\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0166864124002086\",\"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":"Topology and its Applications","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0166864124002086","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
On some applications of property (A) ((σ-A)) at a point
If X is a hereditarily metacompact ω-scattered space and X has a σ-NSR pair-base at every point of X, then X has a σ-NSR pair-base. If X is a hereditarily meta-Lindelöf ω-scattered space and X has a σ-NSR pair-base at every point of X, then X has property (σ-A). If X is a hereditarily meta-Lindelöf GO-space such that every condensation set of X has property (σ-A), then X has property (σ-A). We point out that there is a gap in the proof of Lemma 37 in [18]. We give a detailed proof for the result. We finally show that if is a GO-space and has property (A) for some , then X has property (A), where , is not an isolated point of for each . If X is a hereditarily meta-Lindelöf ω-scattered GO-space, then X has a σ-NSR pair-base and is hereditarily a D-space.
期刊介绍:
Topology and its Applications is primarily concerned with publishing original research papers of moderate length. However, a limited number of carefully selected survey or expository papers are also included. The mathematical focus of the journal is that suggested by the title: Research in Topology. It is felt that it is inadvisable to attempt a definitive description of topology as understood for this journal. Certainly the subject includes the algebraic, general, geometric, and set-theoretic facets of topology as well as areas of interactions between topology and other mathematical disciplines, e.g. topological algebra, topological dynamics, functional analysis, category theory. Since the roles of various aspects of topology continue to change, the non-specific delineation of topics serves to reflect the current state of research in topology.
At regular intervals, the journal publishes a section entitled Open Problems in Topology, edited by J. van Mill and G.M. Reed. This is a status report on the 1100 problems listed in the book of the same name published by North-Holland in 1990, edited by van Mill and Reed.