Timeline for Does -I belong to Weyl group?
Current License: CC BY-SA 3.0
4 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 25, 2012 at 18:20 | comment | added | Jeffrey Adams | Also -I is in the Weyl group if and only if the center of the simply connected group is a 2-group | |
| Nov 29, 2011 at 17:00 | comment | added | Jim Humphreys | In the non-crystallographic cases it seems harder to come up with a useful mnemonic device, though the general criterion is always the same: -1 belongs to the irreducible finite Coxeter group iff all degrees of basic polynomial invariants are even. | |
| Nov 29, 2011 at 13:19 | comment | added | Geordie Williamson | ...or one remembers that it depends on the parity of $D_n$ and uses the case of $D_3 = A_3$ and $D_2 = A_1 \times A_1$ to decide. | |
| Nov 29, 2011 at 12:25 | history | answered | Allen Knutson | CC BY-SA 3.0 |