{"title":"可测函数环上的u-拓扑和m-拓扑,推广和重访","authors":"Sudip Kumar Acharyya, Atasi Debray, Pratip Nandi","doi":"10.1007/s00012-025-00896-6","DOIUrl":null,"url":null,"abstract":"<div><p>Given an ideal <i>I</i> in the ring <span>\\(\\mathcal {M}(X,\\mathcal {A})\\)</span> of all real valued measurable functions over the measurable space <span>\\((X,\\mathcal {A})\\)</span> and a measure <span>\\(\\mu :\\mathcal {A}\\rightarrow [0,\\infty ]\\)</span>, we introduce the <span>\\(u_\\mu ^I\\)</span>-topology and the <span>\\(m_\\mu ^I\\)</span>-topology on <span>\\(\\mathcal {M}(X,\\mathcal {A})\\)</span> as generalizations of the <i>u</i>-topology and the <i>m</i>-topology on <span>\\(\\mathcal {M}(X,\\mathcal {A})\\)</span> respectively. For a countably generated ideal <i>I</i> in <span>\\(\\mathcal {M}(X,\\mathcal {A})\\)</span>, it is proved that the <span>\\(u_\\mu ^I\\)</span>-topology and the <span>\\(m_\\mu ^I\\)</span>-topology coincide if and only if <span>\\(X\\setminus \\bigcap Z[I]\\)</span> is a <span>\\(\\mu \\)</span>-bounded subset of <i>X</i>. The components of 0 in both of these topologies are determined and it is proved that the condition of denseness of an ideal <i>I</i> in <span>\\(\\mathcal {M}(X,\\mathcal {A})\\)</span> is equivalent in these two topologies and this happens when and only when there exists <span>\\(Z\\in Z[I]\\)</span> such that <span>\\(\\mu (Z)=0\\)</span>. It is also proved that <i>I</i> is closed in <span>\\(\\mathcal {M}(X,\\mathcal {A})\\)</span> in the <span>\\(m_\\mu \\)</span>-topology if and only if it is a <span>\\(Z_\\mu \\)</span>-ideal. Two more topologies on <span>\\(\\mathcal {M}(X,\\mathcal {A})\\)</span> viz. the <span>\\(u_{\\mu ,F}^I\\)</span>-topology and the <span>\\(m_{\\mu ,F}^I\\)</span>-topology, finer than the <span>\\(u_\\mu ^I\\)</span>-topology and the <span>\\(m_\\mu ^I\\)</span>-topology respectively are introduced and a few relevant properties are investigated thereon.</p></div>","PeriodicalId":50827,"journal":{"name":"Algebra Universalis","volume":"86 3","pages":""},"PeriodicalIF":0.6000,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"u-topology and m-topology on the ring of measurable functions, generalized and revisited\",\"authors\":\"Sudip Kumar Acharyya, Atasi Debray, Pratip Nandi\",\"doi\":\"10.1007/s00012-025-00896-6\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Given an ideal <i>I</i> in the ring <span>\\\\(\\\\mathcal {M}(X,\\\\mathcal {A})\\\\)</span> of all real valued measurable functions over the measurable space <span>\\\\((X,\\\\mathcal {A})\\\\)</span> and a measure <span>\\\\(\\\\mu :\\\\mathcal {A}\\\\rightarrow [0,\\\\infty ]\\\\)</span>, we introduce the <span>\\\\(u_\\\\mu ^I\\\\)</span>-topology and the <span>\\\\(m_\\\\mu ^I\\\\)</span>-topology on <span>\\\\(\\\\mathcal {M}(X,\\\\mathcal {A})\\\\)</span> as generalizations of the <i>u</i>-topology and the <i>m</i>-topology on <span>\\\\(\\\\mathcal {M}(X,\\\\mathcal {A})\\\\)</span> respectively. For a countably generated ideal <i>I</i> in <span>\\\\(\\\\mathcal {M}(X,\\\\mathcal {A})\\\\)</span>, it is proved that the <span>\\\\(u_\\\\mu ^I\\\\)</span>-topology and the <span>\\\\(m_\\\\mu ^I\\\\)</span>-topology coincide if and only if <span>\\\\(X\\\\setminus \\\\bigcap Z[I]\\\\)</span> is a <span>\\\\(\\\\mu \\\\)</span>-bounded subset of <i>X</i>. The components of 0 in both of these topologies are determined and it is proved that the condition of denseness of an ideal <i>I</i> in <span>\\\\(\\\\mathcal {M}(X,\\\\mathcal {A})\\\\)</span> is equivalent in these two topologies and this happens when and only when there exists <span>\\\\(Z\\\\in Z[I]\\\\)</span> such that <span>\\\\(\\\\mu (Z)=0\\\\)</span>. It is also proved that <i>I</i> is closed in <span>\\\\(\\\\mathcal {M}(X,\\\\mathcal {A})\\\\)</span> in the <span>\\\\(m_\\\\mu \\\\)</span>-topology if and only if it is a <span>\\\\(Z_\\\\mu \\\\)</span>-ideal. Two more topologies on <span>\\\\(\\\\mathcal {M}(X,\\\\mathcal {A})\\\\)</span> viz. the <span>\\\\(u_{\\\\mu ,F}^I\\\\)</span>-topology and the <span>\\\\(m_{\\\\mu ,F}^I\\\\)</span>-topology, finer than the <span>\\\\(u_\\\\mu ^I\\\\)</span>-topology and the <span>\\\\(m_\\\\mu ^I\\\\)</span>-topology respectively are introduced and a few relevant properties are investigated thereon.</p></div>\",\"PeriodicalId\":50827,\"journal\":{\"name\":\"Algebra Universalis\",\"volume\":\"86 3\",\"pages\":\"\"},\"PeriodicalIF\":0.6000,\"publicationDate\":\"2025-06-23\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Algebra Universalis\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s00012-025-00896-6\",\"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":"Algebra Universalis","FirstCategoryId":"100","ListUrlMain":"https://link.springer.com/article/10.1007/s00012-025-00896-6","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
u-topology and m-topology on the ring of measurable functions, generalized and revisited
Given an ideal I in the ring \(\mathcal {M}(X,\mathcal {A})\) of all real valued measurable functions over the measurable space \((X,\mathcal {A})\) and a measure \(\mu :\mathcal {A}\rightarrow [0,\infty ]\), we introduce the \(u_\mu ^I\)-topology and the \(m_\mu ^I\)-topology on \(\mathcal {M}(X,\mathcal {A})\) as generalizations of the u-topology and the m-topology on \(\mathcal {M}(X,\mathcal {A})\) respectively. For a countably generated ideal I in \(\mathcal {M}(X,\mathcal {A})\), it is proved that the \(u_\mu ^I\)-topology and the \(m_\mu ^I\)-topology coincide if and only if \(X\setminus \bigcap Z[I]\) is a \(\mu \)-bounded subset of X. The components of 0 in both of these topologies are determined and it is proved that the condition of denseness of an ideal I in \(\mathcal {M}(X,\mathcal {A})\) is equivalent in these two topologies and this happens when and only when there exists \(Z\in Z[I]\) such that \(\mu (Z)=0\). It is also proved that I is closed in \(\mathcal {M}(X,\mathcal {A})\) in the \(m_\mu \)-topology if and only if it is a \(Z_\mu \)-ideal. Two more topologies on \(\mathcal {M}(X,\mathcal {A})\) viz. the \(u_{\mu ,F}^I\)-topology and the \(m_{\mu ,F}^I\)-topology, finer than the \(u_\mu ^I\)-topology and the \(m_\mu ^I\)-topology respectively are introduced and a few relevant properties are investigated thereon.
期刊介绍:
Algebra Universalis publishes papers in universal algebra, lattice theory, and related fields. In a pragmatic way, one could define the areas of interest of the journal as the union of the areas of interest of the members of the Editorial Board. In addition to research papers, we are also interested in publishing high quality survey articles.