{"title":"Vector bundles on bielliptic surfaces: Ulrich bundles and degree of irrationality","authors":"Edoardo Mason","doi":"10.1002/mana.70103","DOIUrl":"https://doi.org/10.1002/mana.70103","url":null,"abstract":"<p>This paper deals with two problems about vector bundles on bielliptic surfaces. The first is to give a classification of Ulrich bundles on such surfaces <span></span><math>\u0000 <semantics>\u0000 <mi>S</mi>\u0000 <annotation>$S$</annotation>\u0000 </semantics></math>, which depends on the topological type of <span></span><math>\u0000 <semantics>\u0000 <mi>S</mi>\u0000 <annotation>$S$</annotation>\u0000 </semantics></math>. In doing so, we study the weak Brill–Noether property for moduli spaces of sheaves with isotropic Mukai vector. Adapting an idea of Moretti [21], we also interpret the problem of determining the degree of irrationality of bielliptic surfaces in terms of the existence of certain stable vector bundles of rank 2, completing the work of Yoshihara.</p>","PeriodicalId":49853,"journal":{"name":"Mathematische Nachrichten","volume":"299 3","pages":"514-528"},"PeriodicalIF":0.8,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mana.70103","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147570346","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":"(\u0000 N\u0000 ,\u0000 q\u0000 )\u0000 \u0000 $(N,q)$\u0000 -Laplacian equations with one-sided critical exponential growth","authors":"Elisandra Gloss, Hector Pereira, Bruno Ribeiro","doi":"10.1002/mana.70116","DOIUrl":"https://doi.org/10.1002/mana.70116","url":null,"abstract":"<p>We prove the existence of two non-trivial weak solutions for a class of quasilinear, non-homogeneous elliptic problems driven by the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mi>N</mi>\u0000 <mo>,</mo>\u0000 <mi>q</mi>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation>$(N,q)$</annotation>\u0000 </semantics></math>-Laplacian with one-sided critical exponential growth in a bounded domain <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>Ω</mi>\u0000 <mo>⊂</mo>\u0000 <msup>\u0000 <mi>R</mi>\u0000 <mi>N</mi>\u0000 </msup>\u0000 </mrow>\u0000 <annotation>$Omega subset mathbb {R}^{N}$</annotation>\u0000 </semantics></math>. The first solution is obtained as a local minimizer of the associated energy functional; to justify this, we establish that any local minimum in the <span></span><math>\u0000 <semantics>\u0000 <msup>\u0000 <mi>C</mi>\u0000 <mn>1</mn>\u0000 </msup>\u0000 <annotation>$C^{1}$</annotation>\u0000 </semantics></math> topology is also a local minimum in the natural <span></span><math>\u0000 <semantics>\u0000 <msup>\u0000 <mi>W</mi>\u0000 <mrow>\u0000 <mn>1</mn>\u0000 <mo>,</mo>\u0000 <mi>N</mi>\u0000 </mrow>\u0000 </msup>\u0000 <annotation>$W^{1,N}$</annotation>\u0000 </semantics></math> topology. This minimization result is proved in a more general setting and may be useful in related problems. The second solution is given by <i>minimax</i> methods.</p>","PeriodicalId":49853,"journal":{"name":"Mathematische Nachrichten","volume":"299 3","pages":"675-698"},"PeriodicalIF":0.8,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mana.70116","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147566136","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}