{"title":"自反巴拿赫空间中可服从群拟表示的一个平凡定理的推论","authors":"A. I. Shtern","doi":"10.1134/S106192082204015X","DOIUrl":null,"url":null,"abstract":"<p> As is known, for a sufficiently small defect of a (not necessarily bounded) quasirepresentation of an amenable group in a reflexive Banach space <span>\\(E\\)</span> with dense set of bounded orbits, there is an extension of this quasirepresentation for which there is a close ordinary representation of the group in the space of this extension. In the present note it is proved that, if the original quasirepresentation <span>\\(\\pi\\)</span> of an amenable group <span>\\(G\\)</span> in a reflexive Banach space <span>\\(E\\)</span> is a pseudorepresentation, then an ordinary representation of <span>\\(G\\)</span>, in the vector subspace <span>\\(L\\)</span> of <span>\\(E\\)</span> formed by vectors with bounded orbits and equipped with a natural Banach norm, which is close to <span>\\(\\pi|_L\\)</span> (this ordinary representation exists if the defect of <span>\\(\\pi\\)</span> is sufficiently small) is equivalent to <span>\\(\\pi|_L\\)</span>. </p>","PeriodicalId":763,"journal":{"name":"Russian Journal of Mathematical Physics","volume":null,"pages":null},"PeriodicalIF":1.7000,"publicationDate":"2023-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"A Corollary to a Triviality Theorem for Quasirepresentations of an Amenable Group in Reflexive Banach Spaces\",\"authors\":\"A. I. Shtern\",\"doi\":\"10.1134/S106192082204015X\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p> As is known, for a sufficiently small defect of a (not necessarily bounded) quasirepresentation of an amenable group in a reflexive Banach space <span>\\\\(E\\\\)</span> with dense set of bounded orbits, there is an extension of this quasirepresentation for which there is a close ordinary representation of the group in the space of this extension. In the present note it is proved that, if the original quasirepresentation <span>\\\\(\\\\pi\\\\)</span> of an amenable group <span>\\\\(G\\\\)</span> in a reflexive Banach space <span>\\\\(E\\\\)</span> is a pseudorepresentation, then an ordinary representation of <span>\\\\(G\\\\)</span>, in the vector subspace <span>\\\\(L\\\\)</span> of <span>\\\\(E\\\\)</span> formed by vectors with bounded orbits and equipped with a natural Banach norm, which is close to <span>\\\\(\\\\pi|_L\\\\)</span> (this ordinary representation exists if the defect of <span>\\\\(\\\\pi\\\\)</span> is sufficiently small) is equivalent to <span>\\\\(\\\\pi|_L\\\\)</span>. </p>\",\"PeriodicalId\":763,\"journal\":{\"name\":\"Russian Journal of Mathematical Physics\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.7000,\"publicationDate\":\"2023-01-24\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Russian Journal of Mathematical Physics\",\"FirstCategoryId\":\"101\",\"ListUrlMain\":\"https://link.springer.com/article/10.1134/S106192082204015X\",\"RegionNum\":3,\"RegionCategory\":\"物理与天体物理\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"PHYSICS, MATHEMATICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Russian Journal of Mathematical Physics","FirstCategoryId":"101","ListUrlMain":"https://link.springer.com/article/10.1134/S106192082204015X","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSICS, MATHEMATICAL","Score":null,"Total":0}
A Corollary to a Triviality Theorem for Quasirepresentations of an Amenable Group in Reflexive Banach Spaces
As is known, for a sufficiently small defect of a (not necessarily bounded) quasirepresentation of an amenable group in a reflexive Banach space \(E\) with dense set of bounded orbits, there is an extension of this quasirepresentation for which there is a close ordinary representation of the group in the space of this extension. In the present note it is proved that, if the original quasirepresentation \(\pi\) of an amenable group \(G\) in a reflexive Banach space \(E\) is a pseudorepresentation, then an ordinary representation of \(G\), in the vector subspace \(L\) of \(E\) formed by vectors with bounded orbits and equipped with a natural Banach norm, which is close to \(\pi|_L\) (this ordinary representation exists if the defect of \(\pi\) is sufficiently small) is equivalent to \(\pi|_L\).
期刊介绍:
Russian Journal of Mathematical Physics is a peer-reviewed periodical that deals with the full range of topics subsumed by that discipline, which lies at the foundation of much of contemporary science. Thus, in addition to mathematical physics per se, the journal coverage includes, but is not limited to, functional analysis, linear and nonlinear partial differential equations, algebras, quantization, quantum field theory, modern differential and algebraic geometry and topology, representations of Lie groups, calculus of variations, asymptotic methods, random process theory, dynamical systems, and control theory.