Timeline for is the induced map of an embedding an Iso on Ext-groups?
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 18, 2019 at 8:23 | vote | accept | Felix | ||
| Jan 17, 2019 at 21:12 | answer | added | Sasha | timeline score: 2 | |
| Jan 17, 2019 at 14:58 | comment | added | Felix | thanks a lot! then I will give up that hope. | |
| Jan 17, 2019 at 14:56 | comment | added | Sam Gunningham | A simple counterexample is given by the inclusion $pt \hookrightarrow \mathbb P^1$ (we might just as well replace $\mathbb P^1$ with $\mathbb A^1$). Obviously the ext groups are trivial on a point, but the skyscraper sheaf does have higher self-exts, as computed by the Koszul complex. I expect that your map is almost never an isomorphism for this reason. | |
| Jan 17, 2019 at 14:47 | history | edited | Felix | CC BY-SA 4.0 |
added 2 characters in body
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| Jan 17, 2019 at 14:42 | history | asked | Felix | CC BY-SA 4.0 |