{"title":"代数群的对映模:归纳和投影盖","authors":"Dylan Johnston","doi":"10.1016/j.jalgebra.2024.10.019","DOIUrl":null,"url":null,"abstract":"<div><div>In this paper we investigate contramodules for algebraic groups. Namely, we give contramodule analogs to two <span><math><msup><mrow><mn>20</mn></mrow><mrow><mtext>th</mtext></mrow></msup></math></span> century results about comodules. Firstly, we show that induction of contramodules over coordinate rings of algebraic groups is exact if and only if the associated quotient variety is affine. Secondly, we give an inverse limit theorem for constructing projective covers of simple <em>G</em>-modules using <em>G</em>-structures of projective covers of simple modules of the first Frobenius kernel, <span><math><msub><mrow><mi>G</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>. We conclude by showing that the inverse limit theorem is a special case of a more general phenomenon between injective covers in <span><math><mi>k</mi><mo>[</mo><mi>G</mi><mo>]</mo></math></span>-Comod and projective covers in <span><math><mi>k</mi><mo>[</mo><mi>G</mi><mo>]</mo></math></span>-Contra.</div></div>","PeriodicalId":0,"journal":{"name":"","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Contramodules for algebraic groups: Induction and projective covers\",\"authors\":\"Dylan Johnston\",\"doi\":\"10.1016/j.jalgebra.2024.10.019\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>In this paper we investigate contramodules for algebraic groups. Namely, we give contramodule analogs to two <span><math><msup><mrow><mn>20</mn></mrow><mrow><mtext>th</mtext></mrow></msup></math></span> century results about comodules. Firstly, we show that induction of contramodules over coordinate rings of algebraic groups is exact if and only if the associated quotient variety is affine. Secondly, we give an inverse limit theorem for constructing projective covers of simple <em>G</em>-modules using <em>G</em>-structures of projective covers of simple modules of the first Frobenius kernel, <span><math><msub><mrow><mi>G</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span>. We conclude by showing that the inverse limit theorem is a special case of a more general phenomenon between injective covers in <span><math><mi>k</mi><mo>[</mo><mi>G</mi><mo>]</mo></math></span>-Comod and projective covers in <span><math><mi>k</mi><mo>[</mo><mi>G</mi><mo>]</mo></math></span>-Contra.</div></div>\",\"PeriodicalId\":0,\"journal\":{\"name\":\"\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0,\"publicationDate\":\"2024-10-22\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S002186932400560X\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S002186932400560X","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
摘要
在本文中,我们研究了代数群的反模子。也就是说,我们给出了等映模与 20 世纪关于逗点的两个结果的对应关系。首先,我们证明了代数群坐标环上的反模量归纳是精确的,当且仅当相关商综是仿射的。其次,我们给出了一个逆极限定理,利用第一弗罗本尼乌斯核的简单模块 G1 的投影盖的 G 结构,构造简单 G 模块的投影盖。最后,我们证明了逆极限定理是 k[G]-Comod 中的注入盖和 k[G]-Contra 中的投影盖之间更普遍现象的特例。
Contramodules for algebraic groups: Induction and projective covers
In this paper we investigate contramodules for algebraic groups. Namely, we give contramodule analogs to two century results about comodules. Firstly, we show that induction of contramodules over coordinate rings of algebraic groups is exact if and only if the associated quotient variety is affine. Secondly, we give an inverse limit theorem for constructing projective covers of simple G-modules using G-structures of projective covers of simple modules of the first Frobenius kernel, . We conclude by showing that the inverse limit theorem is a special case of a more general phenomenon between injective covers in -Comod and projective covers in -Contra.