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Aug 4, 2017 at 23:09 history edited YCor
edited tags
Aug 4, 2017 at 19:59 answer added Will Sawin timeline score: 4
Aug 4, 2017 at 19:39 history edited Grobber CC BY-SA 3.0
edited text
Aug 4, 2017 at 2:47 comment added Grobber I am not sure why the problem could be reduced to the affine case.
Aug 3, 2017 at 22:34 comment added მამუკა ჯიბლაძე By definition, $\mathfrak g$ is a finite subgroup of the automorphism group of $X$, so it acts by automorphisms on $X$, and $X$ is in the case considered $\operatorname{Spec}A$
Aug 3, 2017 at 18:58 comment added Grobber But why does $\mathfrak{g}$ act on $\operatorname{Spec} A$?
Aug 3, 2017 at 18:51 comment added მამუკა ჯიბლაძე Evidently $G$ is an isomorphic copy of $\mathfrak g$ acting on $A$. More or less by definition the category of affine $\operatorname{Spec} B$-schemes is opposite to that of $B$-algebras, so naming a subgroup $\mathfrak g$ of the automorphism group of $X=\operatorname{Spec} A$ over $\operatorname{Spec} B$ is the same as naming a(n isomorphic) subgroup $G$ of the automorphism group of the $B$-algebra $A$.
Aug 3, 2017 at 18:14 comment added Grobber I always forget \mathfrak{}
Aug 3, 2017 at 18:13 history edited Grobber CC BY-SA 3.0
added 15 characters in body
Aug 3, 2017 at 18:10 comment added M.G. The notation is \mathfrak{} (Fraktur "g"). I hope you don't mind me fixing it for you.
S Aug 3, 2017 at 18:09 history suggested M.G. CC BY-SA 3.0
fixed latex for g
Aug 3, 2017 at 18:08 review Suggested edits
S Aug 3, 2017 at 18:09
Aug 3, 2017 at 18:05 history asked Grobber CC BY-SA 3.0