Timeline for Why are unramified maps not required to be locally of finite presentation?
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
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| Jun 15, 2020 at 7:27 | history | edited | CommunityBot |
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| May 12, 2015 at 9:33 | vote | accept | jmc | ||
| May 11, 2015 at 21:33 | answer | added | David Rydh | timeline score: 34 | |
| May 1, 2015 at 19:33 | comment | added | Marc Hoyois | @jmc Well, you usually want closed immersions to be proper, that's what I had in mind. A specific situation where properness turns out to be appropriate is in the proper base change theorem (in $\ell$-adic cohomology, say): there's no need for finite presentability there. | |
| May 1, 2015 at 17:26 | comment | added | jmc | @LaurentMoret-Bailly — Ok, I can see that that should be reasonable. But that alone seems not very convincing yet… | |
| May 1, 2015 at 17:22 | comment | added | jmc | @MarcHoyois — Could you expand on that? If I recall correctly I've once heard Bas Edixhoven say that proper maps should have been defined to be of finite presentation. I really don't know what the morally correct definition should be. I would love to be enlightened. | |
| May 1, 2015 at 15:13 | comment | added | Marc Hoyois | You similarly don't want to require proper maps to be of finite presentation. | |
| May 1, 2015 at 13:20 | comment | added | Laurent Moret-Bailly | For one thing, it seems reasonable that all immersions should be unramified. | |
| May 1, 2015 at 12:22 | history | asked | jmc | CC BY-SA 3.0 |