{"title":"Interpolation of derivatives and ultradifferentiable regularity","authors":"Armin Rainer, Gerhard Schindl","doi":"10.1002/mana.202300567","DOIUrl":"https://doi.org/10.1002/mana.202300567","url":null,"abstract":"<p>Interpolation inequalities for <span></span><math>\u0000 <semantics>\u0000 <msup>\u0000 <mi>C</mi>\u0000 <mi>m</mi>\u0000 </msup>\u0000 <annotation>$C^m$</annotation>\u0000 </semantics></math> functions allow to bound derivatives of intermediate order <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>0</mn>\u0000 <mo><</mo>\u0000 <mi>j</mi>\u0000 <mo><</mo>\u0000 <mi>m</mi>\u0000 </mrow>\u0000 <annotation>$0 < j<m$</annotation>\u0000 </semantics></math> by bounds for the derivatives of order 0 and <span></span><math>\u0000 <semantics>\u0000 <mi>m</mi>\u0000 <annotation>$m$</annotation>\u0000 </semantics></math>. We review various interpolation inequalities for <span></span><math>\u0000 <semantics>\u0000 <msup>\u0000 <mi>L</mi>\u0000 <mi>p</mi>\u0000 </msup>\u0000 <annotation>$L^p$</annotation>\u0000 </semantics></math>-norms (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>1</mn>\u0000 <mo>≤</mo>\u0000 <mi>p</mi>\u0000 <mo>≤</mo>\u0000 <mi>∞</mi>\u0000 </mrow>\u0000 <annotation>$1 le p le infty$</annotation>\u0000 </semantics></math>) in arbitrary finite dimensions. They allow us to study ultradifferentiable regularity by lacunary estimates in a comprehensive way, striving for minimal assumptions on the weights.</p>","PeriodicalId":49853,"journal":{"name":"Mathematische Nachrichten","volume":"298 2","pages":"617-635"},"PeriodicalIF":0.8,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mana.202300567","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143396828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The \u0000 \u0000 \u0000 R\u0000 ∞\u0000 \u0000 $R_infty$\u0000 -property and commensurability for nilpotent groups","authors":"Maarten Lathouwers, Thomas Witdouck","doi":"10.1002/mana.202400154","DOIUrl":"https://doi.org/10.1002/mana.202400154","url":null,"abstract":"<p>For finitely generated torsion-free nilpotent groups, the associated Mal'cev Lie algebra of the group is used frequently when studying the <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mi>R</mi>\u0000 <mi>∞</mi>\u0000 </msub>\u0000 <annotation>$R_infty$</annotation>\u0000 </semantics></math>-property. Two such groups have isomorphic Mal'cev Lie algebras if and only if they are abstractly commensurable. We show that the <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mi>R</mi>\u0000 <mi>∞</mi>\u0000 </msub>\u0000 <annotation>$R_infty$</annotation>\u0000 </semantics></math>-property is not invariant under abstract commensurability within the class of finitely generated torsion-free nilpotent groups by providing counterexamples within a class of 2-step nilpotent groups associated to edge-weighted graphs. These groups are abstractly commensurable to 2-step nilpotent quotients of right-angled Artin groups.</p>","PeriodicalId":49853,"journal":{"name":"Mathematische Nachrichten","volume":"298 2","pages":"602-616"},"PeriodicalIF":0.8,"publicationDate":"2024-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143397074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}