{"title":"Nonstandard representation of the Dirichlet form and application to the comparison theorem","authors":"Haosui Duanmu, Aaron Smith","doi":"10.1002/mana.202300246","DOIUrl":"https://doi.org/10.1002/mana.202300246","url":null,"abstract":"<p>The Dirichlet form is a generalization of the Laplacian, heavily used in the study of many diffusion-like processes. In this paper, we present a <i>nonstandard representation theorem</i> for the Dirichlet form, showing that the usual Dirichlet form can be well-approximated by a <i>hyperfinite</i> sum. One of the main motivations for such a result is to provide a tool for directly translating results about Dirichlet forms on finite or countable state spaces to results on more general state spaces, without having to translate the details of the proofs. As an application, we compare the Dirichlet forms of two general Markov processes by applying the transfer of the well-known comparison theorem for finite Markov processes.</p>","PeriodicalId":49853,"journal":{"name":"Mathematische Nachrichten","volume":"298 4","pages":"1167-1183"},"PeriodicalIF":0.8,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mana.202300246","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809762","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}
David P. Blecher, Matthew Neal, Antonio M. Peralta, Shanshan Su
{"title":"M\u0000 $M$\u0000 -Ideals in real operator algebras","authors":"David P. Blecher, Matthew Neal, Antonio M. Peralta, Shanshan Su","doi":"10.1002/mana.202400227","DOIUrl":"https://doi.org/10.1002/mana.202400227","url":null,"abstract":"<p>In a recent paper, we showed that a subspace of a real <span></span><math>\u0000 <semantics>\u0000 <msup>\u0000 <mi>JBW</mi>\u0000 <mo>∗</mo>\u0000 </msup>\u0000 <annotation>${rm JBW}^*$</annotation>\u0000 </semantics></math>-triple is an <span></span><math>\u0000 <semantics>\u0000 <mi>M</mi>\u0000 <annotation>$M$</annotation>\u0000 </semantics></math>-summand if and only if it is a <span></span><math>\u0000 <semantics>\u0000 <msup>\u0000 <mi>weak</mi>\u0000 <mo>∗</mo>\u0000 </msup>\u0000 <annotation>${rm weak}^*$</annotation>\u0000 </semantics></math>-closed triple ideal. As a consequence, <span></span><math>\u0000 <semantics>\u0000 <mi>M</mi>\u0000 <annotation>$M$</annotation>\u0000 </semantics></math>-ideals of real <span></span><math>\u0000 <semantics>\u0000 <msup>\u0000 <mi>JB</mi>\u0000 <mo>∗</mo>\u0000 </msup>\u0000 <annotation>${rm JB}^*$</annotation>\u0000 </semantics></math>-triples, including real <span></span><math>\u0000 <semantics>\u0000 <msup>\u0000 <mi>C</mi>\u0000 <mo>∗</mo>\u0000 </msup>\u0000 <annotation>${rm C}^*$</annotation>\u0000 </semantics></math>-algebras, real <span></span><math>\u0000 <semantics>\u0000 <msup>\u0000 <mi>JB</mi>\u0000 <mo>∗</mo>\u0000 </msup>\u0000 <annotation>${rm JB}^*$</annotation>\u0000 </semantics></math>-algebras and real TROs, correspond to norm-closed triple ideals. In this paper, we extend this result by identifying the <span></span><math>\u0000 <semantics>\u0000 <mi>M</mi>\u0000 <annotation>$M$</annotation>\u0000 </semantics></math>-ideals in (possibly non-self-adjoint) real operator algebras and Jordan operator algebras. The argument for this is necessarily different. We also give simple characterizations of one-sided <span></span><math>\u0000 <semantics>\u0000 <mi>M</mi>\u0000 <annotation>$M$</annotation>\u0000 </semantics></math>-ideals in real operator algebras, and give some applications to that theory.</p>","PeriodicalId":49853,"journal":{"name":"Mathematische Nachrichten","volume":"298 4","pages":"1328-1341"},"PeriodicalIF":0.8,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809763","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}