Timeline for Epimorphisms from an affine scheme?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Apr 13, 2019 at 4:17 | comment | added | Piotr Achinger | Let us continue this discussion in chat. | |
| Apr 13, 2019 at 4:11 | comment | added | user137767 | Other than that, yes it appears that your logic works | |
| Apr 13, 2019 at 4:11 | comment | added | user137767 | @PiotrAchinger Eric Wofsey says you need some reducedness assumption for density: math.stackexchange.com/questions/2378504/… | |
| Apr 13, 2019 at 4:02 | comment | added | Piotr Achinger | By the way, is there an example of a morphism as in the question which is not surjective (so that the result from Stacks Project does not apply)? Integral implies closed, and the image is dense, so it should be surjective. | |
| Apr 13, 2019 at 4:00 | comment | added | Piotr Achinger | @StepanBanach You are right, I didn't notice this assumption! Of course my examples are not integral. | |
| Apr 13, 2019 at 0:53 | comment | added | user137767 | @PiotrAchinger is your morphism really integral? I kind of have hard time reconciling your claim with this: stacks.math.columbia.edu/tag/05YU | |
| Apr 12, 2019 at 20:00 | comment | added | Piotr Achinger | @aginensky yes, that works too. | |
| Apr 12, 2019 at 18:32 | comment | added | meh | Or how about F = elliptic curve E less a pt and FxF -> E being group addition ? Won't that work too ? | |
| Apr 12, 2019 at 16:54 | comment | added | Piotr Achinger | See also: en.wikipedia.org/wiki/Jouanolou%27s_trick | |
| Apr 12, 2019 at 16:54 | comment | added | Piotr Achinger | No, take $X=\mathbf{A}^2 \setminus C$ where $C$ is a curve passing through $0$ which does not contain a line. Then we have a surjection $X\to \mathbf{P}^1$. | |
| Apr 12, 2019 at 13:30 | review | First posts | |||
| Apr 12, 2019 at 14:13 | |||||
| Apr 12, 2019 at 13:27 | history | asked | schematic_boi | CC BY-SA 4.0 |