現代数学の系譜工学物理雑談古典ガロア理論も読む80

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176: 現代数学の系譜 雑談 古典ガロア理論も読む ◆e.a0E5TtKE  [] 2020/01/08(水) 12:15:31.15 ID:1QCooAdl

>>175 追加

IUTその4に下記説明ある
が、圏論で筋通した方が良さそう？

P72
Example 3.2. Categories. The notions of a [small] category and an isomorphism class of [covariant] functors between two given [small] categories yield an
example of a species. That is to say, at a set-theoretic level, one may think of a
[small] category as, for instance, a set of arrows, together with a set of composition
relations, that satisfies certain properties; one may think of a [covariant] functor
between [small] categories as the set given by the graph of the map on arrows determined by the functor [which satisfies certain properties]; one may think of an
isomorphism class of functors as a collection of such graphs, i.e., the graphs determined by the functors in the isomorphism class, which satisfies certain properties.
Then one has “dictionaries”
0-species ←→ the notion of a category
1-species ←→ the notion of an isomorphism class of functors
at the level of notions and
a 0-specimen ←→ a particular [small] category
a 1-specimen ←→ a particular isomorphism class of functors
at the level of specific mathematical objects in a specific ZFC-model. Moreover, one
verifies easily that species-isomorphisms between 0-species correspond to isomorphism classes of equivalences of categories in the usual sense.

Remark 3.2.1. Note that in the case of Example 3.2, one could also define a
notion of “2-species”, “2-specimens”, etc., via the notion of an “isomorphism of
functors”, and then take the 1-species under consideration to be the notion of a
functor [i.e., not an isomorphism class of functors]. Indeed, more generally, one
could define a notion of “n-species” for arbitrary integers n ? 1. Since, however,
this approach would only serve to add an unnecessary level of complexity to the
theory, we choose here to take the approach of working with “functors considered up to isomorphism”.

http://rio2016.5ch.net/test/read.cgi/math/1578091012/176

177: 現代数学の系譜 雑談 古典ガロア理論も読む ◆e.a0E5TtKE  [] 2020/01/08(水) 19:04:57.09 ID:1QCooAdl

>>175 追加
species って、wikipedia では、下記 Combinatorial species なのだが、望月先生と同じ意味か？
Andre Joyal 抜きには語れないようだが、望月 IUT4には Joyal先生の名前が出てこない（＾＾；

https://en.wikipedia.org/wiki/Combinatorial_species
Combinatorial species
(抜粋)
In combinatorial mathematics, the theory of combinatorial species is an abstract, systematic method for analysing discrete structures in terms of generating functions.
Examples of discrete structures are (finite) graphs, permutations, trees, and so on; each of these has an associated generating function which counts how many structures there are of a certain size.
One goal of species theory is to be able to analyse complicated structures by describing them in terms of transformations and combinations of simpler structures.

https://en.wikipedia.org/wiki/Andr%C3%A9_Joyal
(抜粋)
Andre Joyal (born 1943) is a professor of mathematics at the Universite du Quebec a Montreal who works on category theory. He was a member of the School of Mathematics at the Institute for Advanced Study in 2013,[1] where he was invited to join the Special Year on Univalent Foundations of Mathematics.[2]

Research
He discovered Kripke?Joyal semantics,[3] the theory of combinatorial species and with Myles Tierney a generalization of the Galois theory of Alexander Grothendieck[4] in the setup of locales. Most of his research is in some way related to category theory, higher category theory and their applications.
He did some work on quasi-categories, after their invention by Michael Boardman and Rainer Vogt, in particular conjecturing[5] and proving the existence of a Quillen model structure on sSet whose weak equivalences generalize both equivalence of categories and Kan equivalence of spaces.
He co-authored the book "Algebraic Set Theory" with Ieke Moerdijk and recently started a web-based expositional project Joyal's CatLab [6] on categorical mathematics.

http://rio2016.5ch.net/test/read.cgi/math/1578091012/177

636: 現代数学の系譜 雑談 古典ガロア理論も読む ◆e.a0E5TtKE  [] 2020/01/13(月) 15:28:47.40 ID:vKumeiVN

>>189
>＞望月先生が、IUTその4の”species”で、何を言わんとしているのかなー？
>グロタンディエック宇宙じゃなく、望月宇宙とかさ
>「ZFCくそくらえ」と言いましょうよ、望月先生！！

ZFCから独立な命題の一覧（下記）
IUTが、ZFC内なのだと？
”species”使って言い訳しているみたいだが、ちょっと変
（>>175 に書いたけど、”species”は圏論でしょ？）
もっと、「圏論で何が悪い」と堂々と主張する方がいいと思うけど
ZFCは、完全じゃないんだから（＾＾；

（参考）
https://ja.wikipedia.org/wiki/ZFC%E3%81%8B%E3%82%89%E7%8B%AC%E7%AB%8B%E3%81%AA%E5%91%BD%E9%A1%8C%E3%81%AE%E4%B8%80%E8%A6%A7
ZFCから独立な命題の一覧
(抜粋)
・フビニの定理の拡張[10]
・ある種のディオファントス方程式の解の存在[11]
・群論におけるホワイトヘッドの問題（英語版）(シェラハ、1974年) - A を任意のアーベル群とするとき、Ext1(A, Z) = 0 ならば A は自由アーベル群か？
[11] https://projecteuclid.org/download/pdf_1/euclid.bams/1183547548
James P. Jones (1980). “Undecidable diophantine equations”. Bull. Amer. Math. Soc. 3 (2): 859?862. doi:10.1090/s0273-0979-1980-14832-6.

https://en.wikipedia.org/wiki/List_of_statements_independent_of_ZFC
List of statements independent of ZFC
(抜粋)
Number theory
One can write down a concrete polynomial p ∈ Z[x1,...x9] such that the statement "there are integers m1,...,m9 with p(m1,...,m9)=0" can neither be proven nor disproven in ZFC (assuming ZFC is consistent).[16][17][circular reference]
This follows from Yuri Matiyasevich's resolution of Hilbert's tenth problem; the polynomial is constructed so that it has an integer root if and only if ZFC is inconsistent[18].

[18] https://link.springer.com/article/10.1007/s10958-014-1830-2 (2014)
"ON A DIOPHANTINE REPRESENTATION OF THE PREDICATE OF PROVABILITY". Journal of Mathematical Sciences.

http://rio2016.5ch.net/test/read.cgi/math/1578091012/636

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