{"title":"The first-countability in generalizations of topological groups with ideal convergence","authors":"Xin Liu, Shou Lin, Xiangeng Zhou","doi":"10.1016/j.topol.2024.109150","DOIUrl":null,"url":null,"abstract":"<div><div>The study of convergence in topological groups has become a frontier research subject. In many cases, the first-countability is an important and strong condition. Based on <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>s</mi><mi>n</mi></mrow></msub></math></span>-continuity, the present paper discusses how topology and algebra are related through a notion of continuity generated by ideal convergence. We introduce the classes of generalizations of topological groups, give the structures of <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>s</mi><mi>n</mi></mrow></msub></math></span>-topological groups by certain sequential coreflections, and obtain generalized metric properties of <span><math><mi>I</mi></math></span>-<em>snf</em>-countable para-<span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>s</mi><mi>n</mi></mrow></msub></math></span>-topological groups.</div><div>Let <span><math><mi>I</mi></math></span> be an admissible ideal on the set <span><math><mi>N</mi></math></span> of natural numbers. The following results are obtained.<ul><li><span>(1)</span><span><div>Every T<sub>2</sub>, <span><math><mi>I</mi></math></span>-<em>snf</em>-countable para-<span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>s</mi><mi>n</mi></mrow></msub></math></span>-topological group is an <em>sn</em>-quasi-metrizable and <em>cs</em>-submetrizable space.</div></span></li><li><span>(2)</span><span><div>A T<sub>0</sub>, <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>s</mi><mi>n</mi></mrow></msub></math></span>-topological group is an <span><math><mi>I</mi></math></span>-<em>snf</em>-countable space if and only if it is a <em>cs</em>-metrizable space satisfying that each sequentially open subset is <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>s</mi><mi>n</mi></mrow></msub></math></span>-open.</div></span></li></ul></div><div>These show the unique role of <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>s</mi><mi>n</mi></mrow></msub></math></span>-continuity in the study of topological groups and related structures, and present a version of topological algebra using the notion of ideals.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"360 ","pages":"Article 109150"},"PeriodicalIF":0.6000,"publicationDate":"2025-02-01","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/S0166864124003353","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
Abstract
The study of convergence in topological groups has become a frontier research subject. In many cases, the first-countability is an important and strong condition. Based on -continuity, the present paper discusses how topology and algebra are related through a notion of continuity generated by ideal convergence. We introduce the classes of generalizations of topological groups, give the structures of -topological groups by certain sequential coreflections, and obtain generalized metric properties of -snf-countable para--topological groups.
Let be an admissible ideal on the set of natural numbers. The following results are obtained.
(1)
Every T2, -snf-countable para--topological group is an sn-quasi-metrizable and cs-submetrizable space.
(2)
A T0, -topological group is an -snf-countable space if and only if it is a cs-metrizable space satisfying that each sequentially open subset is -open.
These show the unique role of -continuity in the study of topological groups and related structures, and present a version of topological algebra using the notion of ideals.
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.