Timeline for Are open $\mathbb{G}_m$-invariant subschemes of an affine scheme precisely the homogeneous radical ideals of its coordinate ring?
Current License: CC BY-SA 4.0
4 events
| when toggle format | what | by | license | comment | |
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| Jan 28, 2020 at 22:12 | vote | accept | Jakob Werner | ||
| Jan 28, 2020 at 13:24 | comment | added | Will Sawin | @MartinBrandenburg Then the maps $\mathbb G_m \times X\to X$ are not smooth, and in particular the inverse image of a reduced closed subscheme can clearly be non-reduced. I think this approach does work for general smooth group schemes. | |
| Jan 28, 2020 at 9:49 | comment | added | Martin Brandenburg | Where does this use the special case $\mathbb{G}_m$? Angelo wrote that it is false for general group schemes. | |
| Jan 28, 2020 at 1:18 | history | answered | Will Sawin | CC BY-SA 4.0 |