{"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":0,"journal":{"name":"","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1007/s00010-024-01077-x","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","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。