Timeline for Example of an Algebraic Space ("false" affine line with different tangents at origin)
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
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| Apr 27, 2021 at 15:28 | comment | added | Dan Petersen | Yes, that's precisely my reading. | |
| Apr 27, 2021 at 15:10 | vote | accept | user267839 | ||
| Apr 27, 2021 at 15:10 | comment | added | user267839 | ...and then we take for $U$ the dual numbers $D=Spec(k[\epsilon])$, since $F(D)$ represent with the tangent vectors of this presheaf, that finishes the argument, right? | |
| Apr 27, 2021 at 14:50 | comment | added | Dan Petersen | What Skjelnes is using is that if $F$ is a separated presheaf of sets, then $F(U)\to LF(U)$ is injective. So separated presheaves have the property that sections map injectively into the sheafification. | |
| Apr 27, 2021 at 14:43 | comment | added | user267839 | oh yes sorry, you are right, that's page 5, I overlooked it. But I still not understand how this fact that the presheaf quotient is separated in the sense above, implies that the tangent directions must also appear in sheaf quotient (if it would exist). | |
| Apr 27, 2021 at 13:59 | history | edited | Dan Petersen | CC BY-SA 4.0 |
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| Apr 27, 2021 at 13:45 | history | edited | Dan Petersen | CC BY-SA 4.0 |
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| Apr 27, 2021 at 13:40 | history | answered | Dan Petersen | CC BY-SA 4.0 |