Timeline for What is the difference between PSL_2 and PGL_2?
Current License: CC BY-SA 2.5
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 24, 2010 at 21:24 | comment | added | BCnrd | Kevin, you mean "over global fields", right? :) Anyway, I taught myself about algebraic groups to better understand the automorphic stuff. But this PSL_n business doesn't involve anything serious about algebraic groups, just general quotient nonsense from SGA3 which is relevant for fppf/etale sheaves in general. I learned the serious parts in a better way during my recent work on pseudo-reductive groups (which, to my amusement, seems to be a handy reference for over 50% of what I respond to on this website). Care to ask a question about smooth unipotent groups over imperfect fields? :) | |
| Feb 24, 2010 at 20:31 | comment | added | Kevin Buzzard | Heh, well, I guess I'm letting slip where my interests lie :-) Whyever you are learning this stuff? I'm trying to teach myself automorphic forms over number fields. | |
| Feb 24, 2010 at 1:06 | comment | added | BCnrd | Kevin, one other thing: I just checked out P-R from the library, and I am reminded that they assume from the outset that their ground field is characteristic 0! Really a shame. :) | |
| Feb 23, 2010 at 17:05 | comment | added | BCnrd | Kevin, if you recommend Platonov-Rapinchuk to your students, just warn them to assume everything is affine in the discussion of adelic points there. Their exposition on adelic points claims to avoid affineness hypotheses, but what they define is actually not well-defined in such generality (so doesn't work for G/B and so forth). | |
| Feb 23, 2010 at 17:01 | history | edited | BCnrd | CC BY-SA 2.5 |
added 30 characters in body
|
| Feb 23, 2010 at 16:55 | comment | added | Kevin Buzzard | Just to clarify: for anyone who thinks "pah, who thinks about non-perfect fields anyway", the answer is absolutely that the theory of connected reductive groups over fields like k(T) and k((T)), k finite, are an integral part of the Langlands programme, and neither of these fields are perfect. To Brian: I've found Platonov-Rapinchuk quite readable. It took me a long time to find a book that wasn't SGA3 but which did reductive groups over fields in a way I understood. | |
| Feb 23, 2010 at 16:43 | history | edited | BCnrd | CC BY-SA 2.5 |
added 149 characters in body
|
| Feb 23, 2010 at 16:30 | history | answered | BCnrd | CC BY-SA 2.5 |