{"title":"If <i>R<sup>m</sup></i> ≅ <i>R<sup>n</sup></i> must <i>m</i> = <i>n</i>?","authors":"Tyrone Crisp","doi":"10.1080/00029890.2023.2184163","DOIUrl":null,"url":null,"abstract":"A fundamental theorem of linear algebra asserts that every basis for the vector space Rn has n elements. In this expository note we present a theorem of W. G. Leavitt describing one way in which this invariant basis number property can fail when one does linear algebra over rings, rather than over fields. We give a proof of Leavitt’s theorem that combines ideas of P. M. Cohn and A. L. S. Corner into an elementary form requiring only a nodding acquaintance with matrices and modular arithmetic.","PeriodicalId":7761,"journal":{"name":"American Mathematical Monthly","volume":"11 1","pages":"0"},"PeriodicalIF":0.4000,"publicationDate":"2023-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"American Mathematical Monthly","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1080/00029890.2023.2184163","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
A fundamental theorem of linear algebra asserts that every basis for the vector space Rn has n elements. In this expository note we present a theorem of W. G. Leavitt describing one way in which this invariant basis number property can fail when one does linear algebra over rings, rather than over fields. We give a proof of Leavitt’s theorem that combines ideas of P. M. Cohn and A. L. S. Corner into an elementary form requiring only a nodding acquaintance with matrices and modular arithmetic.
线性代数的一个基本定理断言向量空间Rn的每一组基有n个元素。在这篇说述性的笔记中,我们提出了W. G. Leavitt的一个定理,该定理描述了当人们在环上而不是在域上做线性代数时,这个不变基数性质可能失效的一种方式。我们给出了莱维特定理的一个证明,这个证明结合了P. M. Cohn和a . L. S. Corner的思想,形成了一个初等的形式,只需要对矩阵和模运算略知一知。
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