Timeline for Quasi-affineness of the base of a $\mathbb{G}_a$-torsor
Current License: CC BY-SA 3.0
6 events
| when toggle format | what | by | license | comment | |
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| Aug 14, 2014 at 21:08 | comment | added | David E Speyer | One strategy to prove that $Y$ is quasi-affine would be to show that $Y \to \mathrm{Spec}(A_0)$ is etale and of generic degree $1$, where $A_0$ is the ring of invariant functions. I think that should force an open immersion when $Y$ is separated, while having a good chance of being true even when $Y$ isn't. | |
| Aug 14, 2014 at 19:43 | comment | added | Torsten Wedhorn | @David: Thank you very much for the example and the references. Of course, I will accept your answer. But I would like to wait a little hoping to attract more people to the modified question. | |
| Aug 14, 2014 at 19:38 | comment | added | Torsten Wedhorn | @Alexander: In my situation I do know a priori that $Y$ is separated. Hence I would be very grateful if you could elaborate. | |
| Aug 14, 2014 at 19:06 | comment | added | Alexander Braverman | Actually, I suspect that the answer might be yes, if you assume that $Y$ is separated. | |
| Aug 14, 2014 at 17:23 | history | edited | David E Speyer | CC BY-SA 3.0 |
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| Aug 14, 2014 at 17:10 | history | answered | David E Speyer | CC BY-SA 3.0 |