[過去ﾛｸﾞ] 現代数学の系譜 工学物理雑談 古典ガロア理論も読む49 (658ﾚｽ)
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67(1): 現代数学の系譜 雑談 古典ガロア理論も読む ◆e.a0E5TtKE [sage] 2018/01/01(月) 17:07:53.69 ID:dCRrvhl7(3/27) AAS
で、勝手ながら、年末年始に読んだ関連を貼るよ（＾＾

まず、関連参考：検索でヒットしたので貼る。
BaireCategory.pdfの”3. Pointwise limits of continuous functions.”に、「422に書いた定理」の関連記述
「Theorem. If f : R → R is a pointwise limit of continuous functions,
then Df is Fσ meager (that is, a countable union of closed sets with empty interior).
(In particular, by Baire's theorem, f is continuous on a dense subset of R.)」とあり（当たり前か？ （＾＾ ）

http://www.math.utk.edu/~freire/teaching/m447f16/m447f16index.html
MATH 447- Advanced Calculus I- Fall 2016- A. FREIRE
(or: ANALYSIS IN R^n)
(抜粋)
http://www.math.utk.edu/~freire/teaching/m447f16/BaireCategory.pdf
Sets of discontinuity and Baire's theorem Baire Category Notes (5 problems) (the problems are HW8, due Friday 11/4)A. FREIRE 2016
(抜粋)
1. Sets of discontinuity. For f : R → R, we define
Df = {x ∈ R; f is not continuous at xg:

3. Pointwise limits of continuous functions.
Theorem. If f : R → R is a pointwise limit of continuous functions,
then Df is Fσ meager (that is, a countable union of closed sets with empty interior).
(In particular, by Baire's theorem, f is continuous on a dense subset of R.)

Proof. We know Df = ∪ n>=1 D1/n (see Section 1), so it suffices to show
that the closed sets Dε have empty interior, for any ε > 0.
By contradiction, suppose Dε contains an open interval I.
We'll find an open interval J ⊂ I disjoint from Dε!
Let fn → f pointwise on R, with each fn : R → R continuous.
For each N >= 1, consider the set:
CN = {x ∈ I; (∀m, n >= N)|fm(x) - fn(x)| <= ε/3}.
Clearly ∪ N>=1 CN = I (by pointwise convergence). QED
(引用終り)

つづく

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68(1): 現代数学の系譜 雑談 古典ガロア理論も読む ◆e.a0E5TtKE [sage] 2018/01/01(月) 17:08:32.82 ID:dCRrvhl7(4/27) AAS
>>67 つづき

（上記の関連参考：出典URL）
http://www.math.utk.edu/~freire/teaching/m447f16/m447f16topics.html
Math 447 Fall 2016- A. FREIRE
TOPICS
PART I: Topology

Supplementary handouts (for advanced students):
(adapted from more advanced classes and not yet in final form)

http://www.math.utk.edu/~freire/teaching/m447f16/GeneralTopologyReview.pdf
Definitions and Theorems from General Topology

http://www.math.utk.edu/~freire/teaching/m447f16/BanachSpace.pdf
Locally compact Banach spaces are finite dimensional (includes 4 problems)

http://www.math.utk.edu/~freire/teaching/m447f16/SpacesOfContinuousFunctions.pdf
Spaces of Continuous Functions (outdated)

http://www.math.utk.edu/~freire/teaching/m447f16/StoneWeierstrassNotes.pdf
Stone-Weierstrass theorem-notes (includes 6 problems)

http://www.math.utk.edu/~freire/teaching/m447f16/AscoliArzelaNotes.pdf
Ascoli-Arzela-Notes (final-included 7 exercises with solutions, and 11 extra problems.)

http://www.math.utk.edu/~freire/teaching/
Alex Freire
Department of Mathematics
University of Tennessee
（終り）

つづく

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