{"title":"Abelian absolute Galois groups","authors":"Moshe Jarden","doi":"10.1017/s0017089524000028","DOIUrl":null,"url":null,"abstract":"Generalizing a result of Wulf-Dieter Geyer in his thesis, we prove that if <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0017089524000028_inline1.png\" /> <jats:tex-math> $K$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> is a finitely generated extension of transcendence degree <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0017089524000028_inline2.png\" /> <jats:tex-math> $r$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> of a global field and <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0017089524000028_inline3.png\" /> <jats:tex-math> $A$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> is a closed abelian subgroup of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0017089524000028_inline4.png\" /> <jats:tex-math> $\\textrm{Gal}(K)$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, then <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0017089524000028_inline5.png\" /> <jats:tex-math> ${\\mathrm{rank}}(A)\\le r+1$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. Moreover, if <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0017089524000028_inline6.png\" /> <jats:tex-math> $\\mathrm{char}(K)=0$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, then <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0017089524000028_inline7.png\" /> <jats:tex-math> ${\\hat{\\mathbb{Z}}}^{r+1}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> is isomorphic to a closed subgroup of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0017089524000028_inline8.png\" /> <jats:tex-math> $\\textrm{Gal}(K)$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>.","PeriodicalId":50417,"journal":{"name":"Glasgow Mathematical Journal","volume":"9 1","pages":""},"PeriodicalIF":0.5000,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Glasgow Mathematical Journal","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1017/s0017089524000028","RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
Generalizing a result of Wulf-Dieter Geyer in his thesis, we prove that if $K$ is a finitely generated extension of transcendence degree $r$ of a global field and $A$ is a closed abelian subgroup of $\textrm{Gal}(K)$ , then ${\mathrm{rank}}(A)\le r+1$ . Moreover, if $\mathrm{char}(K)=0$ , then ${\hat{\mathbb{Z}}}^{r+1}$ is isomorphic to a closed subgroup of $\textrm{Gal}(K)$ .
期刊介绍:
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