Tagged Questions

3
votes
1answer
128 views

‘Generalised’ coinvariant algebras

Let $\mathfrak{g}$ be a simple complex Lie algebra, and $\mathfrak{h}\subset\mathfrak{g}$ a Cartan subalgebra with Weyl group $W$. Consider the fibre product $\mathfrak{h}\times_{\ …
0
votes
0answers
72 views

Weyl group an maximal tori

Consider the group $G = GL(\overline{\mathbb{F}_p}^n)$, and the Torus $T$ of diagonal matrices. Then the Weyl-Group $W = N_G(T)/T$ is isomorphic to $S_n$. Now there is a correspond …
2
votes
0answers
117 views

Edge graph of the polytope of a Bruhat interval

Let $\Gamma$ be a Coxeter group on some generating set $S$, with reflection representation $V$. Then $\Gamma$ has two standard partial orders, the weak and strong Bruhat orders. M …
2
votes
2answers
202 views

For a Weyl group, what is the connection between its exponents and lengths of its elements?

The following seems to be true: if $|W_q| := \sum {q^{l(w)}}$, where the sum is taken over the elements $w$, then $|W_q| = \prod {(1 + q +...+ q^{e_i})}$, where the product is take …
7
votes
4answers
425 views

About the intrinsic definition of the Weyl group of complex semisimple Lie algebras

It may be a easy question for experts. The definition of the Weyl group of a complex semisimple Lie algebra $\mathfrak{g}$ is well-known: We first $\textbf{choose}$ a Cartan suba …
3
votes
2answers
291 views

Weyl group of a singular torus

Let $G$ be a semisimple algebraic group over an algebraically closed field, and let $T$ be a torus in $G$. If $T$ is a maximal torus, then $N_G(T)/Z_G(T)=N_G(T)/T$ is the Weyl gro …
2
votes
2answers
222 views

Software for drawing intervals in Weyl groups

I am looking for an automated way to draw diagrams of intervals in Weyl groups and in their various subsets such as minimal representatives of cosets $W/W_p$ for a parabolic Weyl g …
9
votes
6answers
1k views

Polynomial invariants of the exceptional Weyl groups

Let $\mathfrak{g}$ be a simple complex Lie algebra, and let $\mathfrak{h} \subset \mathfrak{g}$ be a fixed Cartan subalgebra. Let $W$ be the Weyl group associated to $\mathfrak{g}$ …
3
votes
3answers
502 views

Does -I belong to Weyl group?

Let $\Phi$ be an irreducible root system, with positive roots $\Phi^+$ relative to the base $\Delta$. If $W$ is the Weyl group, how can I determine if $-I$ belongs to $W$? Equivale …
2
votes
0answers
125 views

Cell modules for type D Weyl group

Does anyone know a reference for the construction of cell modules for the Weyl group of type $D$, without any reference to the Weyl group of type $B$? What would be even better is …
4
votes
3answers
764 views

Longest element of a Weyl group

Let $G$ an algebraic (reductive) group. $T$ a maximal torus, $B$ a Borel subgroup containing $T$, and $w_0$ the longest element of the Weyl group. I'm looking for a reference expl …
20
votes
5answers
3k views

Definitions of Hecke algebras

There is a definition of Iwahori-Hecke algebras for Coxeter groups in terms of generators and relations and there is a definition of Hecke algebras involving functions on locally c …
7
votes
5answers
939 views

Inverting the Weyl Character Formula

The Weyl Character formula tells us how to write the character of a representation as a linear combination of integral weights. Since characters are invariant under the action of t …
6
votes
3answers
345 views

Occurrences of a simple reflection in the longest element of a Weyl group?

While looking at a preprint I've just bumped into a question about the longest element $w_0$ of a Weyl group $W$ (say irreducible of a Lie type $A$ - $G$ and of rank $n>1$, to …
8
votes
4answers
629 views

Longest Element of an Affine Weyl Group

I know that the Weyl groups of affine Lie algebras don't have a longest element, but are there any good substitutes for w_0. In particular, is there any good substitute for a reduc …

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