{"title":"Uniqueness of embeddings of the affine line into algebraic groups","authors":"P. Feller, Immanuel Stampfli","doi":"10.1090/JAG/725","DOIUrl":null,"url":null,"abstract":"<p>Let <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper Y\">\n <mml:semantics>\n <mml:mi>Y</mml:mi>\n <mml:annotation encoding=\"application/x-tex\">Y</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> be the underlying variety of a complex connected affine algebraic group. We prove that two embeddings of the affine line <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"double-struck upper C\">\n <mml:semantics>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi mathvariant=\"double-struck\">C</mml:mi>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">\\mathbb {C}</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> into <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper Y\">\n <mml:semantics>\n <mml:mi>Y</mml:mi>\n <mml:annotation encoding=\"application/x-tex\">Y</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> are the same up to an automorphism of <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper Y\">\n <mml:semantics>\n <mml:mi>Y</mml:mi>\n <mml:annotation encoding=\"application/x-tex\">Y</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> provided that <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper Y\">\n <mml:semantics>\n <mml:mi>Y</mml:mi>\n <mml:annotation encoding=\"application/x-tex\">Y</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> is not isomorphic to a product of a torus <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"left-parenthesis double-struck upper C Superscript asterisk Baseline right-parenthesis Superscript k\">\n <mml:semantics>\n <mml:mrow>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:msup>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi mathvariant=\"double-struck\">C</mml:mi>\n </mml:mrow>\n <mml:mo>∗<!-- ∗ --></mml:mo>\n </mml:msup>\n <mml:msup>\n <mml:mo stretchy=\"false\">)</mml:mo>\n <mml:mi>k</mml:mi>\n </mml:msup>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">(\\mathbb {C}^\\ast )^k</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> and one of the three varieties <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"double-struck upper C cubed\">\n <mml:semantics>\n <mml:msup>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi mathvariant=\"double-struck\">C</mml:mi>\n </mml:mrow>\n <mml:mn>3</mml:mn>\n </mml:msup>\n <mml:annotation encoding=\"application/x-tex\">\\mathbb {C}^3</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula>, <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper S upper L 2\">\n <mml:semantics>\n <mml:msub>\n <mml:mi>SL</mml:mi>\n <mml:mn>2</mml:mn>\n </mml:msub>\n <mml:annotation encoding=\"application/x-tex\">\\operatorname {SL}_2</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula>, and <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper P upper S upper L 2\">\n <mml:semantics>\n <mml:msub>\n <mml:mi>PSL</mml:mi>\n <mml:mn>2</mml:mn>\n </mml:msub>\n <mml:annotation encoding=\"application/x-tex\">\\operatorname {PSL}_2</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula>.</p>","PeriodicalId":54887,"journal":{"name":"Journal of Algebraic Geometry","volume":"1 1","pages":""},"PeriodicalIF":0.9000,"publicationDate":"2016-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1090/JAG/725","citationCount":"8","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Algebraic Geometry","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1090/JAG/725","RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 8
Abstract
Let YY be the underlying variety of a complex connected affine algebraic group. We prove that two embeddings of the affine line C\mathbb {C} into YY are the same up to an automorphism of YY provided that YY is not isomorphic to a product of a torus (C∗)k(\mathbb {C}^\ast )^k and one of the three varieties C3\mathbb {C}^3, SL2\operatorname {SL}_2, and PSL2\operatorname {PSL}_2.
期刊介绍:
The Journal of Algebraic Geometry is devoted to research articles in algebraic geometry, singularity theory, and related subjects such as number theory, commutative algebra, projective geometry, complex geometry, and geometric topology.
This journal, published quarterly with articles electronically published individually before appearing in an issue, is distributed by the American Mathematical Society (AMS). In order to take advantage of some features offered for this journal, users will occasionally be linked to pages on the AMS website.