{"title":"涉及弱紧性的一些性质,IV:通过密集子空间定义的类紧性性质","authors":"J.A. Martínez-Cadena , Á. Tamariz-Mascarúa","doi":"10.1016/j.topol.2025.109487","DOIUrl":null,"url":null,"abstract":"<div><div>We study several compactness-like properties arising from the existence of dense subspaces satisfying relative compactness conditions, namely: <em>countably pracompact</em>, <em>totally countably pracompact</em>, <em>densely ω-bounded</em>, and <em>sequentially pracompact</em> spaces. These classes refine classical notions such as sequential compactness and <em>ω</em>-boundedness and admit a natural hierarchy. We establish various preservation results for these properties under perfect open mappings and product spaces. In the context of topological groups, we prove that if <em>H</em> is a locally compact subgroup of a topological group <em>G</em>, then the corresponding quotient mapping <span><math><mi>π</mi><mo>:</mo><mi>G</mi><mo>→</mo><mi>G</mi><mo>/</mo><mi>H</mi></math></span> allows the transfer of local versions of these properties from <span><math><mi>G</mi><mo>/</mo><mi>H</mi></math></span> to <em>G</em>. We also analyze the extent to which these properties satisfy the <em>three-space property</em> and introduce the class of <em>PC-spaces</em> to characterize when such transfer is possible. Finally, we address structural questions on densely <em>ω</em>-bounded paratopological groups and provide conditions under which they are topological.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"373 ","pages":"Article 109487"},"PeriodicalIF":0.5000,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Some properties involving feeble compactness, IV: Compactness-like properties defined via dense subspaces\",\"authors\":\"J.A. Martínez-Cadena , Á. Tamariz-Mascarúa\",\"doi\":\"10.1016/j.topol.2025.109487\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>We study several compactness-like properties arising from the existence of dense subspaces satisfying relative compactness conditions, namely: <em>countably pracompact</em>, <em>totally countably pracompact</em>, <em>densely ω-bounded</em>, and <em>sequentially pracompact</em> spaces. These classes refine classical notions such as sequential compactness and <em>ω</em>-boundedness and admit a natural hierarchy. We establish various preservation results for these properties under perfect open mappings and product spaces. In the context of topological groups, we prove that if <em>H</em> is a locally compact subgroup of a topological group <em>G</em>, then the corresponding quotient mapping <span><math><mi>π</mi><mo>:</mo><mi>G</mi><mo>→</mo><mi>G</mi><mo>/</mo><mi>H</mi></math></span> allows the transfer of local versions of these properties from <span><math><mi>G</mi><mo>/</mo><mi>H</mi></math></span> to <em>G</em>. We also analyze the extent to which these properties satisfy the <em>three-space property</em> and introduce the class of <em>PC-spaces</em> to characterize when such transfer is possible. Finally, we address structural questions on densely <em>ω</em>-bounded paratopological groups and provide conditions under which they are topological.</div></div>\",\"PeriodicalId\":51201,\"journal\":{\"name\":\"Topology and its Applications\",\"volume\":\"373 \",\"pages\":\"Article 109487\"},\"PeriodicalIF\":0.5000,\"publicationDate\":\"2025-06-26\",\"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/S0166864125002858\",\"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/S0166864125002858","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
Some properties involving feeble compactness, IV: Compactness-like properties defined via dense subspaces
We study several compactness-like properties arising from the existence of dense subspaces satisfying relative compactness conditions, namely: countably pracompact, totally countably pracompact, densely ω-bounded, and sequentially pracompact spaces. These classes refine classical notions such as sequential compactness and ω-boundedness and admit a natural hierarchy. We establish various preservation results for these properties under perfect open mappings and product spaces. In the context of topological groups, we prove that if H is a locally compact subgroup of a topological group G, then the corresponding quotient mapping allows the transfer of local versions of these properties from to G. We also analyze the extent to which these properties satisfy the three-space property and introduce the class of PC-spaces to characterize when such transfer is possible. Finally, we address structural questions on densely ω-bounded paratopological groups and provide conditions under which they are topological.
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.