{"title":"直纹法诺上的瞬时轮轴是皮卡德等级2和索引1的3倍","authors":"Ozhan Genc , Marcos Jardim","doi":"10.1016/j.jalgebra.2025.07.051","DOIUrl":null,"url":null,"abstract":"<div><div>We study rank 2 <em>h</em>-instanton sheaves on projective threefolds. We demonstrate that any orientable rank 2, non-locally free <em>h</em>-instanton sheaf with defect 0 on a threefold can be obtained as an elementary transformation of a locally free <em>h</em>-instanton sheaf. Our focus then shifts to ruled Fano threefolds of Picard rank 2 and index 1, of which there are five deformation classes. We establish the existence of orientable rank 2 <em>h</em>-instanton bundles on such varieties. Additionally, we prove the existence of Ulrich bundles on such varieties, which correspond to <em>h</em>-instanton sheaves of minimum charge.</div></div>","PeriodicalId":14888,"journal":{"name":"Journal of Algebra","volume":"685 ","pages":"Pages 579-607"},"PeriodicalIF":0.8000,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Instanton sheaves on ruled Fano 3-folds of Picard rank 2 and index 1\",\"authors\":\"Ozhan Genc , Marcos Jardim\",\"doi\":\"10.1016/j.jalgebra.2025.07.051\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>We study rank 2 <em>h</em>-instanton sheaves on projective threefolds. We demonstrate that any orientable rank 2, non-locally free <em>h</em>-instanton sheaf with defect 0 on a threefold can be obtained as an elementary transformation of a locally free <em>h</em>-instanton sheaf. Our focus then shifts to ruled Fano threefolds of Picard rank 2 and index 1, of which there are five deformation classes. We establish the existence of orientable rank 2 <em>h</em>-instanton bundles on such varieties. Additionally, we prove the existence of Ulrich bundles on such varieties, which correspond to <em>h</em>-instanton sheaves of minimum charge.</div></div>\",\"PeriodicalId\":14888,\"journal\":{\"name\":\"Journal of Algebra\",\"volume\":\"685 \",\"pages\":\"Pages 579-607\"},\"PeriodicalIF\":0.8000,\"publicationDate\":\"2025-08-13\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Algebra\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0021869325004661\",\"RegionNum\":2,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Algebra","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0021869325004661","RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
Instanton sheaves on ruled Fano 3-folds of Picard rank 2 and index 1
We study rank 2 h-instanton sheaves on projective threefolds. We demonstrate that any orientable rank 2, non-locally free h-instanton sheaf with defect 0 on a threefold can be obtained as an elementary transformation of a locally free h-instanton sheaf. Our focus then shifts to ruled Fano threefolds of Picard rank 2 and index 1, of which there are five deformation classes. We establish the existence of orientable rank 2 h-instanton bundles on such varieties. Additionally, we prove the existence of Ulrich bundles on such varieties, which correspond to h-instanton sheaves of minimum charge.
期刊介绍:
The Journal of Algebra is a leading international journal and publishes papers that demonstrate high quality research results in algebra and related computational aspects. Only the very best and most interesting papers are to be considered for publication in the journal. With this in mind, it is important that the contribution offer a substantial result that will have a lasting effect upon the field. The journal also seeks work that presents innovative techniques that offer promising results for future research.