{"title":"选定的文本","authors":"Paula S. Cohen","doi":"10.2307/j.ctv17db3jd.7","DOIUrl":null,"url":null,"abstract":"We give a short and self-contained proof of the Fundamental Theorem of Galois Theory (FTGT) for finite degree extensions. We derive the FTGT (for finite degree extensions) from two statements, denoted (a) and (b). These two statements, and the way they are proved here, go back at least to Emil Artin (precise references are given below). The argument is essentially taken from Chapter II of Emil Artin’s Notre Dame Lectures [A]. More precisely, statement (a) below is implicitly contained in the proof Theorem 10 page 31 of [A], in which the uniqueness up to isomorphism of the splitting field of a polynomial is verified. Artin’s proof shows in fact that, when the roots of the polynomial are distinct, the number of automorphisms of the splitting extension coincides with the degree of the extension. Statement (b) below is proved as Theorem 14 page 42 of [A]. The proof given here (using Artin’s argument) was written with Keith Conrad’s help. Theorem Let E/F be an extension of fields, let a1, . . . , an be distinct generators of E/F such that p := (X − a1) · · · (X − an) is in F [X]. Then • the group G of automorphisms of E/F is finite, • there is a bijective correspondence between the sub-extensions S/F of E/F and the subgroups H of G, and we have S ↔ H ⇐⇒ H = Aut(E/S) ⇐⇒ S = E =⇒ [E : S] = |H|, where E is the fixed subfield of H, where [E : S] is the degree (that is the dimension) of E over S, and where |H| is the order of H.","PeriodicalId":313786,"journal":{"name":"French Film Theory and Criticism, Volume 1","volume":"16 1","pages":"0"},"PeriodicalIF":0.0000,"publicationDate":"2020-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Selected Texts\",\"authors\":\"Paula S. Cohen\",\"doi\":\"10.2307/j.ctv17db3jd.7\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"We give a short and self-contained proof of the Fundamental Theorem of Galois Theory (FTGT) for finite degree extensions. We derive the FTGT (for finite degree extensions) from two statements, denoted (a) and (b). These two statements, and the way they are proved here, go back at least to Emil Artin (precise references are given below). The argument is essentially taken from Chapter II of Emil Artin’s Notre Dame Lectures [A]. More precisely, statement (a) below is implicitly contained in the proof Theorem 10 page 31 of [A], in which the uniqueness up to isomorphism of the splitting field of a polynomial is verified. Artin’s proof shows in fact that, when the roots of the polynomial are distinct, the number of automorphisms of the splitting extension coincides with the degree of the extension. Statement (b) below is proved as Theorem 14 page 42 of [A]. The proof given here (using Artin’s argument) was written with Keith Conrad’s help. Theorem Let E/F be an extension of fields, let a1, . . . , an be distinct generators of E/F such that p := (X − a1) · · · (X − an) is in F [X]. Then • the group G of automorphisms of E/F is finite, • there is a bijective correspondence between the sub-extensions S/F of E/F and the subgroups H of G, and we have S ↔ H ⇐⇒ H = Aut(E/S) ⇐⇒ S = E =⇒ [E : S] = |H|, where E is the fixed subfield of H, where [E : S] is the degree (that is the dimension) of E over S, and where |H| is the order of H.\",\"PeriodicalId\":313786,\"journal\":{\"name\":\"French Film Theory and Criticism, Volume 1\",\"volume\":\"16 1\",\"pages\":\"0\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2020-12-08\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"French Film Theory and Criticism, Volume 1\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.2307/j.ctv17db3jd.7\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"French Film Theory and Criticism, Volume 1","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.2307/j.ctv17db3jd.7","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
给出了有限次扩展下伽罗瓦理论基本定理的一个简短且完备的证明。我们从(a)和(b)两个表述中推导出FTGT(有限次扩展)。这两个表述以及它们在这里的证明方法,至少可以追溯到Emil Artin(精确的参考文献在下面给出)。这个论点基本上摘自埃米尔·阿廷的《巴黎圣母院讲座》第二章[A]。更确切地说,下面的表述(a)隐含地包含在[a]的证明定理10页31中,证明了多项式的分裂域的唯一性直到同构。Artin的证明实际上表明,当多项式的根不同时,分裂扩展的自同构数与扩展的程度一致。下面的表述(b)被证明为[A]第42页的定理14。这里给出的证明(使用Artin的论点)是在Keith Conrad的帮助下编写的。设E/F是域的扩展,设a1,…,可以是不同的E/F生成器,使得p:= (X−a1)···(X−an)在F [X]中。然后•同构的G组E / F是有限的,•之间有一个双射的对应关系复杂年代/ F (E / F和G的子组H, H和S↔⇐⇒H = Aut (E / S)⇐⇒S = E =⇒[E: S] = | | H, H E是固定的子域,在[E: S]的程度(即维度)E / S、H, | |是H。
We give a short and self-contained proof of the Fundamental Theorem of Galois Theory (FTGT) for finite degree extensions. We derive the FTGT (for finite degree extensions) from two statements, denoted (a) and (b). These two statements, and the way they are proved here, go back at least to Emil Artin (precise references are given below). The argument is essentially taken from Chapter II of Emil Artin’s Notre Dame Lectures [A]. More precisely, statement (a) below is implicitly contained in the proof Theorem 10 page 31 of [A], in which the uniqueness up to isomorphism of the splitting field of a polynomial is verified. Artin’s proof shows in fact that, when the roots of the polynomial are distinct, the number of automorphisms of the splitting extension coincides with the degree of the extension. Statement (b) below is proved as Theorem 14 page 42 of [A]. The proof given here (using Artin’s argument) was written with Keith Conrad’s help. Theorem Let E/F be an extension of fields, let a1, . . . , an be distinct generators of E/F such that p := (X − a1) · · · (X − an) is in F [X]. Then • the group G of automorphisms of E/F is finite, • there is a bijective correspondence between the sub-extensions S/F of E/F and the subgroups H of G, and we have S ↔ H ⇐⇒ H = Aut(E/S) ⇐⇒ S = E =⇒ [E : S] = |H|, where E is the fixed subfield of H, where [E : S] is the degree (that is the dimension) of E over S, and where |H| is the order of H.