[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48 (625ﾚｽ)
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116(1): 現代数学の系譜 雑談 古典ガロア理論も読む ◆e.a0E5TtKE [sage] 2017/12/16(土) 14:43:18.58 ID:/2xvBEHK(30/58) AAS
>>110
>(Each co-meager set has c points in every interval.)
"c points"の意味が分らん（＾＾
”critical”か”cotinuous”かな？
118(1): 現代数学の系譜 雑談 古典ガロア理論も読む ◆e.a0E5TtKE [sage] 2017/12/16(土) 15:04:54.86 ID:/2xvBEHK(31/58) AAS
>>116
>"c points"の意味が分らん（＾＾
違うかも知れないが、検索ヒットと他にめぼしいヒットがないので下記を貼る
（下記だと、cは連続濃度の意味だね）
https://mathoverflow.net/questions/102386/is-a-random-subset-of-the-real-numbers-non-measurable-is-the-set-of-measurable
(抜粋)
Is a random subset of the real numbers non-measurable? Is the set of measurable sets measurable?
edited Nov 29 '12 at 22:06
19 answered Jul 16 '12
The answer to your second question (assuming the axiom of choice, to dodge Asaf's comment) is that 2^R/Σ has dimension 2^c, where c=2^?0 is the cardinality of the continuum.
The main ingredient of the proof is a partition of [0,1] into c subsets, each of which intersects every uncountable closed subset of [0,1].
To get such a partition,
first note that there are only c closed subsets of [0,1], so you can list them in a sequence of length (the initial ordinal of cardinality) c in such a way that each closed set is listed c times.
Second, recall that every uncountable closed subset of [0,1] has cardinality c.
Finally, do a transfinite inductive construction of c sets in c steps as follows:
At any step, if the closed set at that position in your list is C and if this is its α-th occurrence in the list,
then put an element of C into the α-th of the sets under construction, being careful to use an element of C that hasn't already been put into another of the sets under construction.
You can be this careful, because fewer than c points have been put into any of your sets in the fewer than c preceding stages, while C has c points to choose from. At the end, if some points in [0,1] remain unassigned to any of the sets under construction, put them into some of these sets arbitrarily, to get a partition of [0,1].
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