{"title":"张量积曲面与二次合","authors":"Matthew Weaver","doi":"10.1016/j.laa.2025.04.020","DOIUrl":null,"url":null,"abstract":"<div><div>For <span><math><mi>U</mi><mo>⊆</mo><msup><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msup><mo>(</mo><msub><mrow><mi>O</mi></mrow><mrow><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup><mo>×</mo><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup></mrow></msub><mo>(</mo><mi>a</mi><mo>,</mo><mi>b</mi><mo>)</mo><mo>)</mo></math></span> a four-dimensional vector space, a basis <span><math><mo>{</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>}</mo></math></span> of <em>U</em> defines a rational map <span><math><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>U</mi></mrow></msub><mo>:</mo><mspace></mspace><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup><mo>×</mo><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup><mo>⇢</mo><msup><mrow><mi>P</mi></mrow><mrow><mn>3</mn></mrow></msup></math></span>. The tensor product surface associated to <em>U</em> is the closed image <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span> of the map <span><math><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span>. These surfaces arise within the field of geometric modelling, in which case it is particularly desirable to obtain the implicit equation of <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span>. In this paper, we study <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span> via the syzygies of the associated bigraded ideal <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>U</mi></mrow></msub><mo>=</mo><mo>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>)</mo></math></span> when <em>U</em> is free of basepoints, i.e. <span><math><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span> is regular. Expanding upon work of Duarte and Schenck <span><span>[12]</span></span> for such ideals with a linear syzygy, we address the case that <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span> has a quadratic syzygy.</div></div>","PeriodicalId":18043,"journal":{"name":"Linear Algebra and its Applications","volume":"720 ","pages":"Pages 350-372"},"PeriodicalIF":1.0000,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Tensor product surfaces and quadratic syzygies\",\"authors\":\"Matthew Weaver\",\"doi\":\"10.1016/j.laa.2025.04.020\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>For <span><math><mi>U</mi><mo>⊆</mo><msup><mrow><mi>H</mi></mrow><mrow><mn>0</mn></mrow></msup><mo>(</mo><msub><mrow><mi>O</mi></mrow><mrow><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup><mo>×</mo><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup></mrow></msub><mo>(</mo><mi>a</mi><mo>,</mo><mi>b</mi><mo>)</mo><mo>)</mo></math></span> a four-dimensional vector space, a basis <span><math><mo>{</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>}</mo></math></span> of <em>U</em> defines a rational map <span><math><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>U</mi></mrow></msub><mo>:</mo><mspace></mspace><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup><mo>×</mo><msup><mrow><mi>P</mi></mrow><mrow><mn>1</mn></mrow></msup><mo>⇢</mo><msup><mrow><mi>P</mi></mrow><mrow><mn>3</mn></mrow></msup></math></span>. The tensor product surface associated to <em>U</em> is the closed image <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span> of the map <span><math><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span>. These surfaces arise within the field of geometric modelling, in which case it is particularly desirable to obtain the implicit equation of <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span>. In this paper, we study <span><math><msub><mrow><mi>X</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span> via the syzygies of the associated bigraded ideal <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>U</mi></mrow></msub><mo>=</mo><mo>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>,</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>)</mo></math></span> when <em>U</em> is free of basepoints, i.e. <span><math><msub><mrow><mi>ϕ</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span> is regular. Expanding upon work of Duarte and Schenck <span><span>[12]</span></span> for such ideals with a linear syzygy, we address the case that <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>U</mi></mrow></msub></math></span> has a quadratic syzygy.</div></div>\",\"PeriodicalId\":18043,\"journal\":{\"name\":\"Linear Algebra and its Applications\",\"volume\":\"720 \",\"pages\":\"Pages 350-372\"},\"PeriodicalIF\":1.0000,\"publicationDate\":\"2025-05-06\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Linear Algebra and its Applications\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0024379525001764\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Linear Algebra and its Applications","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0024379525001764","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS","Score":null,"Total":0}
For a four-dimensional vector space, a basis of U defines a rational map . The tensor product surface associated to U is the closed image of the map . These surfaces arise within the field of geometric modelling, in which case it is particularly desirable to obtain the implicit equation of . In this paper, we study via the syzygies of the associated bigraded ideal when U is free of basepoints, i.e. is regular. Expanding upon work of Duarte and Schenck [12] for such ideals with a linear syzygy, we address the case that has a quadratic syzygy.
期刊介绍:
Linear Algebra and its Applications publishes articles that contribute new information or new insights to matrix theory and finite dimensional linear algebra in their algebraic, arithmetic, combinatorial, geometric, or numerical aspects. It also publishes articles that give significant applications of matrix theory or linear algebra to other branches of mathematics and to other sciences. Articles that provide new information or perspectives on the historical development of matrix theory and linear algebra are also welcome. Expository articles which can serve as an introduction to a subject for workers in related areas and which bring one to the frontiers of research are encouraged. Reviews of books are published occasionally as are conference reports that provide an historical record of major meetings on matrix theory and linear algebra.