{"title":"A converse of Ax-Grothendieck theorem for étale endomorphisms of normal schemes","authors":"Lázaro O. Rodríguez Díaz","doi":"arxiv-2409.12163","DOIUrl":null,"url":null,"abstract":"Given an \\'etale endomorphism of a normal irreducible Noetherian and simply\nconnected scheme, we prove that if the endomorphism is surjective then it is\ninjective. The proof is based on Liu's construction of a Galois cover out of a\nsurjective \\'etale morphism. If we give up of the surjectivity hypothesis and\nsuppose the endomorphism is separated, then we prove that the induced field\nextension is Galois. In the case of an \\'etale endomorphism of the affine space\nover an algebraically closed field of characteristic zero, Campbell's theorem\nimplies that the assumption of surjectivity is superfluous.","PeriodicalId":501063,"journal":{"name":"arXiv - MATH - Algebraic Geometry","volume":"54 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - MATH - Algebraic Geometry","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2409.12163","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Given an \'etale endomorphism of a normal irreducible Noetherian and simply
connected scheme, we prove that if the endomorphism is surjective then it is
injective. The proof is based on Liu's construction of a Galois cover out of a
surjective \'etale morphism. If we give up of the surjectivity hypothesis and
suppose the endomorphism is separated, then we prove that the induced field
extension is Galois. In the case of an \'etale endomorphism of the affine space
over an algebraically closed field of characteristic zero, Campbell's theorem
implies that the assumption of surjectivity is superfluous.