{"title":"A note on ideal C $$^*$$ -completions and amenability","authors":"Tomasz Kochanek","doi":"10.1007/s00010-024-01077-x","DOIUrl":null,"url":null,"abstract":"<p>For a discrete group <i>G</i>, we consider certain ideals <span>\\(\\mathcal {I}\\subset c_0(G)\\)</span> of sequences with prescribed rate of convergence to zero. We show that the equality between the full group C<span>\\(^*\\)</span>-algebra of <i>G</i> and the C<span>\\(^*\\)</span>-completion <span>\\(\\textrm{C}^*_{\\mathcal {I}}(G)\\)</span> in the sense of Brown and Guentner (Bull. London Math. Soc. 45:1181–1193, 2013) implies that <i>G</i> is amenable.\n</p>","PeriodicalId":55611,"journal":{"name":"Aequationes Mathematicae","volume":"156 1","pages":""},"PeriodicalIF":0.9000,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Aequationes Mathematicae","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1007/s00010-024-01077-x","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
For a discrete group G, we consider certain ideals \(\mathcal {I}\subset c_0(G)\) of sequences with prescribed rate of convergence to zero. We show that the equality between the full group C\(^*\)-algebra of G and the C\(^*\)-completion \(\textrm{C}^*_{\mathcal {I}}(G)\) in the sense of Brown and Guentner (Bull. London Math. Soc. 45:1181–1193, 2013) implies that G is amenable.
对于离散群 G,我们考虑了某些序列的理想((\mathcal {I}\subset c_0(G)\) of sequences with prescribed rate of convergence to zero)。我们证明,在布朗和根特纳(Bull. London Math. Soc. 45:1181-1193,2013)的意义上,G 的全群 C\(^*\)-algebra 与 C\(^*\)-completion \(\textrm{C}^*_{mathcal {I}}(G)\)之间的相等性意味着 G 是可封闭的。
期刊介绍:
aequationes mathematicae is an international journal of pure and applied mathematics, which emphasizes functional equations, dynamical systems, iteration theory, combinatorics, and geometry. The journal publishes research papers, reports of meetings, and bibliographies. High quality survey articles are an especially welcome feature. In addition, summaries of recent developments and research in the field are published rapidly.