On the denominators of Young's seminormal basis

Young's seminormal basis vectors and their denominators

We study Young's seminormal basis vectors of the dual Specht modules of the symmetric group, indexed by a certain class of standard tableaux, and their denominators. These vectors include those whose denominators control the splitting of the canonical morphism $Δ(λ+μ) \to Δ(λ) \otimes Δ(μ)$ over $\mathbb{Z}_{(p)}$, where $Δ(ν)$ is the Weyl module of the classical Schur algebra labelled by $ν$.

Jantzen filtration of Weyl modules, product of Young symmetrizers and denominator of Young's seminormal basis

Let $G$ be a connected reductive algebraic group over an algebraically closed field of characteristic $p>0$, $Δ(λ)$ denote the Weyl module of $G$ of highest weight $λ$ and $ι_{λ,μ}:Δ(λ+μ)\to Δ(λ)\otimesΔ(μ)$ be the canonical $G$-morphism. We study the split condition for $ι_{λ,μ}$ over $\mathbb{Z}_{(p)}$, and apply this as an approach to compare the Jantzen filtrations of the Weyl modules $Δ(λ)$ and $Δ(λ+μ)$. In the case when $G$ is of type $A$, we show that the split condition is closely related to the product of certain Young symmetrizers and, under some mild conditions, is further character…

Young's seminormal form and simple modules for $S_n$ in characteristic $p$

We realize the integral Specht modules for the symmetric group $S_n$ as induced modules from the subalgebra of the group algebra generated by the Jucys-Murphy elements. We deduce from this that the simple modules for $FS_n$ are generated by reductions modulo $p$ of the corresponding Jucys-Murphy idempotents.

Transition matrices between Young's natural and seminormal representations

We derive a formula for the entries in the change-of-basis matrix between Young's seminormal and natural representations of the symmetric group. These entries are determined as sums over weighted paths in the weak Bruhat graph on standard tableaux, and we show that they can be computed recursively as the weighted sum of at most two previously-computed entries in the matrix. We generalize our results to work for affine Hecke algebras, Ariki-Koike algebras, Iwahori-Hecke algebras, and complex reflection groups given by the wreath product of a finite cyclic group with the symmetric group.

Projective modules for the symmetric group and Young's seminormal form

We study the representation theory of the symmetric group $S_n$ in positive characteristic $p$. Using features of the LLT-algorithm we give a conjectural description of the projective cover $P(λ)$ of the simple module $D(λ)$ where $λ$ is a $p$-restricted partition such that all ladders of the corresponding ladder partition are of order less than $p$. Inspired by the recent theory of Khovanov-Lauda-Rouquier algebras we explain an algorithm that allows us to verify this conjectural description for $n \leq 15$, at least.

外尔群和Iwahori-Hecke代数的半正规表示

Seminormal representations of Weyl groups and Iwahori-Hecke algebras

本文的目的是描述计算对称群的Young半正规表示的类似物的一般过程。方法是将对称群的群代数中的Jucys-Murphy元推广到任意的外尔群和Iwahori-Hecke代数中。这些元素的组合学允许人们显式地并且经常非常容易地计算不可约表示。本文对$A_n$，$B_n$，$D_n$，$G_2$型的外尔群和Iwahori-Hecke代数作了这些计算.虽然这些计算对于类型$F_4$、$E_6$和$E_7$是可以达到的，但考虑到本文的篇幅，我们将把它推迟到另一项工作中。