Timeline for What's a good example/reference for cohomology classes on Springer fibers that aren't restricted from the flag variety
Current License: CC BY-SA 3.0
4 events
| when toggle format | what | by | license | comment | |
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| Aug 1, 2013 at 10:35 | answer | added | Jim Humphreys | timeline score: 3 | |
| Aug 1, 2013 at 7:44 | comment | added | Geordie Williamson | One easy example is provided by the subregular orbits in non simply laced type. They are isomorphic to subregular Springer fibres in much larger (roughly double) simply laced types ("folding"), and hence $H^2$ cannot be surjective. In general, this restriction map must land in the $A_G(x)$ invariants, so any non-trivial $A_G(x)$ action gives you counter-examples. ($A_G(x)$ is the component group of the centralizer.) | |
| Aug 1, 2013 at 5:18 | comment | added | Jay Taylor | Do you really mean SL_n or GL_n? For GL_n this was proven by Hotta and Springer in "A Specialisation Theorem for ...". However I thought this map is already not surjective for all unipotent elements of SL_n. | |
| Aug 1, 2013 at 0:53 | history | asked | Ben Webster♦ | CC BY-SA 3.0 |