Skip to content

WeylGroupExponents ​

The exponents of the Weyl group of the type: one less than each degree.

WeylGroupExponents(cartanType)The exponents of the Weyl group of the type: one less than each degree.
Typed signatures
TypePackageApplies
(cartan_type) -> list<integer>combinatoricsalways

Domain: Cartan type statistics

Details
  • Defined over CartanType as an expression in _x, evaluated by compute-engine — the definition IS the implementation.
  • Takes a CartanType and nothing else — it reads values against their positions, or walks the orbits, so it needs the bijection. Applying it to a bare list is a type error, not a wrong answer.

Definition

Epsil, as the implementation runs it.

on CartanType, over _x

Apply(
       (ds: list<integer>) => Apply((xs_init: list<integer>) => Fold(
                                                                      (
                                                                        xs: list<integer>,
                                                                        x,
                                                                      ) => Apply(
                                                                                 (xs_next: list<integer>) => xs_next,
                                                                                 Join(xs, [x - 1]),
                                                                               ),
                                                                      xs_init,
                                                                      ds,
                                                                    ), []),
       Range(2, _x[2] + 1, 1) if _x[1] == "A" else Map(
                                                        Function(2i, i),
                                                        Range(1, _x[2]),
                                                      ) if _x[1] == "B" else Map(
                                                                                 Function(2i, i),
                                                                                 Range(1, _x[2]),
                                                                               ) if _x[1] == "C" else Join(
                                                                                                           Filter(
                                                                                                                   Map(Function(2i, i), Range(1, _x[2] - 1)),
                                                                                                                   Function(e < _x[2], e),
                                                                                                                 ),
                                                                                                           [_x[2]],
                                                                                                           Filter(
                                                                                                                   Map(Function(2i, i), Range(1, _x[2] - 1)),
                                                                                                                   Function(e >= _x[2], e),
                                                                                                                 ),
                                                                                                         ) if _x[1] == "D" else ([2, 5, 6, 8, 9, 12] if _x[2] == 6 else [2, 6, 8, 10, 12, 14, 18] if _x[2] == 7 else [2, 8, 12, 14, 18, 20, 24, 30]) if _x[1] == "E" else [2, 6, 8, 12] if _x[1] == "F" else [2, 6],
     )

Examples

Basic #

the type D5D_5

live ↗
InWeylGroupExponents(CartanType⁡((D,5)))\mathrm{WeylGroupExponents}(\operatorname{CartanType}((\text{D},5)))Out[1,3,4,5,7]\bigl\lbrack1, 3, 4, 5, 7\bigr\rbrack

the type E6E_6

live ↗
InWeylGroupExponents(CartanType⁡((E,6)))\mathrm{WeylGroupExponents}(\operatorname{CartanType}((\text{E},6)))Out[1,4,5,7,8,11]\bigl\lbrack1, 4, 5, 7, 8, 11\bigr\rbrack
Properties #

the exponents of B3B_3

live ↗
InWeylGroupExponents(CartanType⁡((B,3)))\mathrm{WeylGroupExponents}(\operatorname{CartanType}((\text{B},3)))Out[1,3,5]\bigl\lbrack1, 3, 5\bigr\rbrack

Known value · Bourbaki, Groupes et algèbres de Lie, chapitre VI, planches I-IX

the exponents of E6E_6

live ↗
InWeylGroupExponents(CartanType⁡((E,6)))\mathrm{WeylGroupExponents}(\operatorname{CartanType}((\text{E},6)))Out[1,4,5,7,8,11]\bigl\lbrack1, 4, 5, 7, 8, 11\bigr\rbrack

Known value · Bourbaki, Groupes et algèbres de Lie, chapitre VI, planches I-IX

the exponents of E8E_8

live ↗
InWeylGroupExponents(CartanType⁡((E,8)))\mathrm{WeylGroupExponents}(\operatorname{CartanType}((\text{E},8)))Out[1,7,11,13,17,19,23,29]\bigl\lbrack1, 7, 11, 13, 17, 19, 23, 29\bigr\rbrack

Known value · Bourbaki, Groupes et algèbres de Lie, chapitre VI, planches I-IX

the exponents of F4F_4

live ↗
InWeylGroupExponents(CartanType⁡(("F",4)))\mathrm{WeylGroupExponents}(\operatorname{CartanType}(("F",4)))Out[1,5,7,11]\bigl\lbrack1, 5, 7, 11\bigr\rbrack

Known value · Bourbaki, Groupes et algèbres de Lie, chapitre VI, planches I-IX

the exponents of G2G_2

live ↗
InWeylGroupExponents(CartanType⁡((G,2)))\mathrm{WeylGroupExponents}(\operatorname{CartanType}((\text{G},2)))Out[1,5]\bigl\lbrack1, 5\bigr\rbrack

Known value · Bourbaki, Groupes et algèbres de Lie, chapitre VI, planches I-IX

About
Examples7