Timeline for What is a special parahoric subgroup?
Current License: CC BY-SA 2.5
9 events
| when toggle format | what | by | license | comment | |
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| Aug 4, 2020 at 2:36 | comment | added | LSpice | I thought you might like to know that your post made another convert to the accessibility of Tits. | |
| Sep 29, 2017 at 7:54 | comment | added | fherzig | You are welcome, Marty! Btw, if $K$ is ramified in the definition of the special unitary group, you can get both $SL_2$ and $PGL_2$ as reductive quotient. | |
| Sep 27, 2017 at 16:28 | comment | added | Marty | Oh -- cool! Thanks @fherzig. At least I should have gotten the rank correct. | |
| Sep 26, 2017 at 10:04 | comment | added | fherzig | Actually, at the special but not non-hyperspecial points the reductive quotient of the special fibre is $U(1,1)$. This follows from Tits 3.5 applied to the unramified extension $K$ (note that over $K$ the torus $S$ has rank 2, so the same is true for the maximal split torus over the residue field). Unfortunately, Tits 3.11 contains a mistake in the unramified case. | |
| Dec 9, 2010 at 8:13 | history | edited | Marty | CC BY-SA 2.5 |
Possible error correction in second to last paragraph.
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| Oct 5, 2010 at 5:29 | comment | added | Marty | Glad to hear it! I hope more people read Tits's article in Corvallis too - it's a real gem, and full of great hard-to-find (outside Bruhat-Tits) examples. I only wish there were more pictures in it. | |
| Oct 5, 2010 at 3:41 | comment | added | Emerton | Dear Marty, You have helped more than one person with this explanation. Thanks! | |
| Oct 4, 2010 at 22:34 | vote | accept | Pete L. Clark | ||
| Oct 4, 2010 at 22:01 | history | answered | Marty | CC BY-SA 2.5 |