Timeline for When quotient stacks (for nonsmooth group) are algebraic and related questions
Current License: CC BY-SA 4.0
5 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Nov 3, 2020 at 22:20 | comment | added | David Roberts♦ | I think this is subsumed by stacks.math.columbia.edu/tag/0DLS, which talks about the case of algebraic spaces and also a further layer of 'relativeness': $X\to Y \to S$ and a group algebraic space $G\to Y$ acting on $X$ over $Y$. | |
| Nov 3, 2020 at 19:43 | comment | added | Slup | @AriyanJavanpeykar I am mainly interested in schemes over fields, but it is very interesting and worth knowing. Thank you. | |
| Nov 3, 2020 at 19:36 | comment | added | Ariyan Javanpeykar | @Slup You might find the following interesting: If I recall correctly, if $G$ is a locally finitely presented group scheme over a scheme $S$, then $BG :=[S/G]$ is algebraic if and only if $G$ is flat. A proof of this can be found on the Stacks Project (but might also have appeared on MO before). | |
| Nov 3, 2020 at 18:33 | comment | added | Slup | It is a beautiful theorem. Thank you. | |
| Nov 3, 2020 at 18:11 | history | answered | Niels | CC BY-SA 4.0 |