Picard Groups of Algebraic Groups and an Affineness Criterion

We prove that an algebraic group over a field $k$ is affine precisely when its Picard group is torsion, and show that in this case the Picard group is finite when $k$ is perfect, and the product of a finite group of order prime to $p$ and a $p$-primary group of finite exponent when $k$ is imperfect...

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Main Author: Rosengarten, Zev
Format: Article
Language:English
Published: Académie des sciences 2023-02-01
Series:Comptes Rendus. Mathématique
Online Access:https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.419/
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author Rosengarten, Zev
author_facet Rosengarten, Zev
author_sort Rosengarten, Zev
collection DOAJ
description We prove that an algebraic group over a field $k$ is affine precisely when its Picard group is torsion, and show that in this case the Picard group is finite when $k$ is perfect, and the product of a finite group of order prime to $p$ and a $p$-primary group of finite exponent when $k$ is imperfect of characteristic $p$.
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institution Kabale University
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publisher Académie des sciences
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series Comptes Rendus. Mathématique
spelling doaj-art-c930b04ec28c47a9874e245501752fa72025-02-07T11:06:36ZengAcadémie des sciencesComptes Rendus. Mathématique1778-35692023-02-01361G255956410.5802/crmath.41910.5802/crmath.419Picard Groups of Algebraic Groups and an Affineness CriterionRosengarten, Zev0Einstein Institute of Mathematics, The Hebrew University of Jerusalem, Edmond J. Safra Campus, 91904, Jerusalem, IsraelWe prove that an algebraic group over a field $k$ is affine precisely when its Picard group is torsion, and show that in this case the Picard group is finite when $k$ is perfect, and the product of a finite group of order prime to $p$ and a $p$-primary group of finite exponent when $k$ is imperfect of characteristic $p$.https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.419/
spellingShingle Rosengarten, Zev
Picard Groups of Algebraic Groups and an Affineness Criterion
Comptes Rendus. Mathématique
title Picard Groups of Algebraic Groups and an Affineness Criterion
title_full Picard Groups of Algebraic Groups and an Affineness Criterion
title_fullStr Picard Groups of Algebraic Groups and an Affineness Criterion
title_full_unstemmed Picard Groups of Algebraic Groups and an Affineness Criterion
title_short Picard Groups of Algebraic Groups and an Affineness Criterion
title_sort picard groups of algebraic groups and an affineness criterion
url https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.419/
work_keys_str_mv AT rosengartenzev picardgroupsofalgebraicgroupsandanaffinenesscriterion