[過去ログ] 現代数学の系譜11 ガロア理論を読む13 [転載禁止]©2ch.net (654レス)
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258
(3): 現代数学の系譜11 ガロア理論を読む 2015/05/01(金)04:22 ID:kLen/OPb(2/7) AAS
>>257 つづき

外部リンク[pdf]:www.maa.org
MATHEMATICS MAGAZINE 1966
AUTOMORPHISMS OF THE COMPLEX NUMBERS
PAUL B. YALE,Pomona College

  One of the best known bits of mathematical folklore is that there are many automorphisms of the field of complex numbers,
i.e .,that the complex numbers can be permuted in many ways (besides the familiar complex conjugation) that preserve addition and multiplication.
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259
(2): 現代数学の系譜11 ガロア理論を読む 2015/05/01(金)05:03 ID:kLen/OPb(3/7) AAS
>>258 つづき

THEOREM 4. If φ is a wild automorphism of C then φ is a discontinuous mapping of the complex plane onto itself;
in fact,φ leaves a dense subset of the real line pointwise fixed but maps the real line onto a dense subset of the plane.

Proof. By Theorem 2,φ leaves Q (a dense subset of the real line!) pointwise fixed.
By Theorem 3 we can choose b∈R such that φ(b) not∈R.
Every neighborhood of b contains a rational number (which is left fixed by φ) and the number b (which is moved by φ); hence φ is discontinuous.
For every pair of rational numbers, q and r,φ(rb+q) =φ(r)φ(b)+φ(q)=rφ(b) +q.
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285
(3): 現代数学の系譜11 ガロア理論を読む 2015/05/04(月)21:19 ID:jADohwWI(4/10) AAS
>>283 訂正

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そういえば、>>258 外部リンク[pdf]:www.maa.org
MATHEMATICS MAGAZINE 1966
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335
(2): 現代数学の系譜11 ガロア理論を読む 2015/05/06(水)09:47 ID:SXg2oFIb(7/21) AAS
>>328 つづき

おっちゃんのために
PAUL B. YALE,Pomona College >>258 より

P137
THEOREM 2. Any isomorphism between sub fields of C extends IQ, the identity map on Q.

THEOREM 3. The only isomorphisms between sub fields of C whose domains include R and which map R into R are IR, Ic, and complex conjugation.

Proof. Let Φ be such an isomorphism, i.e., assume R⊆domain Φ and x∈R
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