Timeline for quasi-affine-ness [closed]
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
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| Feb 15, 2018 at 18:58 | history | closed |
R. van Dobben de Bruyn Stefan Kohl♦ abx Jan-Christoph Schlage-Puchta Pace Nielsen |
Needs details or clarity | |
| Feb 15, 2018 at 17:30 | answer | added | Laurent Moret-Bailly | timeline score: 5 | |
| Feb 15, 2018 at 15:27 | comment | added | Jason Starr | @LaurentMoret-Bailly You are correct. I was using the unipotent radical of a Borel subgroup. | |
| Feb 15, 2018 at 14:02 | answer | added | PiJay | timeline score: 2 | |
| Feb 15, 2018 at 14:00 | comment | added | Laurent Moret-Bailly | I thought $R_u(G)$ was the unipotent radical of $G$. For $G=\mathrm{SL}_2$ it is trivial. | |
| Feb 15, 2018 at 12:58 | history | edited | user111251 | CC BY-SA 3.0 |
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| Feb 15, 2018 at 10:29 | comment | added | Jason Starr | For $G$ equal to $\textbf{SL}_2$, and for $H$ equal to $R_u(G)$, the quotient $G/H$ equals $\mathbb{A}^2\setminus\{(0,0)\}$. This is not affine. Did you intend to ask whether $G/H$ is quasi-affine? | |
| Feb 14, 2018 at 22:53 | review | Close votes | |||
| Feb 15, 2018 at 18:58 | |||||
| Feb 14, 2018 at 19:26 | history | edited | user111251 | CC BY-SA 3.0 |
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| Feb 14, 2018 at 18:53 | history | edited | user111251 | CC BY-SA 3.0 |
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| Feb 14, 2018 at 18:53 | comment | added | Jason Starr | What is your definition of an $\mathbb{A}^n$-fibration? For a separated, finitely presented morphism, the property of being affine can be checked after flat, surjective base change. This can be proved using Serre's criterion for affineness, among other methods, | |
| Feb 14, 2018 at 18:48 | history | edited | user111251 | CC BY-SA 3.0 |
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| Feb 14, 2018 at 18:32 | history | asked | user111251 | CC BY-SA 3.0 |