現代数学の系譜工学物理雑談古典ガロア理論も読む77

[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77 (1002ﾚｽ)
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882: 現代数学の系譜 雑談 古典ガロア理論も読む ◆e.a0E5TtKE  [] 2019/10/16(水) 15:18:31.30 ID:86h80x0A

>>881
つづき

https://en.wikipedia.org/wiki/Group_scheme
Group scheme
(抜粋)
Group schemes that are not algebraic groups play a significant role in arithmetic geometry and algebraic topology, since they come up in contexts of Galois representations and moduli problems.
The initial development of the theory of group schemes was due to Alexander Grothendieck, Michel Raynaud and Michel Demazure in the early 1960s.

Examples
・The multiplicative group Gm has the punctured affine line as its underlying scheme, and as a functor, it sends an S-scheme T to the multiplicative group of invertible global sections of the structure sheaf.
　Algebraic tori form an important class of commutative group schemes, defined either by the property of being locally on S a product of copies of Gm, or as groups of multiplicative type associated to finitely generated free abelian groups.
・For any positive integer n, the group μn is the kernel of the nth power map from Gm to itself. As a functor, it sends any S-scheme T to the group of global sections f of T such that fn = 1.
　Over an affine base such as Spec A, it is the spectrum of A[x]/(x^n?1). If n is not invertible in the base, then this scheme is not smooth. In particular, over a field of characteristic p, μp is not smooth.
(引用終り)
以上

http://rio2016.5ch.net/test/read.cgi/math/1568026331/882

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