Timeline for Higher pushforwards of roots of unity
Current License: CC BY-SA 4.0
3 events
| when toggle format | what | by | license | comment | |
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| Nov 23, 2020 at 19:42 | comment | added | R. van Dobben de Bruyn | They will certainly not be locally constant, and this is in fact the whole point of introducing constructible sheaves. Think about the case of a smooth cubic degenerating to a nodal cubic; then $H^1$ is generically $2$-dimensional but in the special fibre only $1$-dimensional (in fact you can compute $\mathbf{Pic}_C \cong \mathbf G_m$ if $C$ is a nodal cubic). | |
| Nov 23, 2020 at 19:20 | comment | added | abx | It seems that you are assuming $\dim(X)=2$, but this is not mentioned in your post. | |
| Nov 23, 2020 at 18:39 | history | asked | whetham | CC BY-SA 4.0 |