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arXiv 2204.09765math.RT
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单连通Weyl群的2-根

2-roots for simply laced Weyl groups

R. M. Green, Tianyuan Xu

AI总结:

本文提出并研究了Kac-Moody代数正交根对称化张量积构成的“2-根”,证明了单连通Y形Dynkin图Weyl群的反射表示对称平方子模具有由2-根组成的典范基,并揭示了其簇代数列符号相干矩阵表示及完全可约性等结构性质。

摘要:

我们引入并研究了“2-根”,它们是Kac-Moody代数正交根的对称化张量积。我们集中于$W$是具有$n$个顶点且包含任意有限长度$a$、$b$和$c$三条分支的单连通Y形Dynkin图$Y_{a,b,c}$的Weyl群的情况;其特例包括$D_n$型、$E_n$型(对于任意$n \geq 6$)以及仿射$E_6$、$E_7$和$E_8$型。我们证明,$W$反射表示的对称平方中一个自然的余维数$1$子模$M$具有一个由2-根组成的非凡典范基$\mathcal{B}$。我们证明,关于$\mathcal{B}$,$W$的每个元素都由簇代数意义上的列符号相干矩阵表示。如果$W$是有限单连通Weyl群,每个2-根的$W$-轨道都有一个最高元素,类似于最高根,我们显式计算了这些元素。我们证明,如果$W$不是仿射型,模$M$在特征零下是完全可约的,且其每个非平凡直和分量均由2-根的$W$-轨道张成。

英文摘要:

We introduce and study "2-roots", which are symmetrized tensor products of orthogonal roots of Kac--Moody algebras. We concentrate on the case where $W$ is the Weyl group of a simply laced Y-shaped Dynkin diagram $Y_{a,b,c}$ having $n$ vertices and with three branches of arbitrary finite lengths $a$, $b$ and $c$; special cases of this include types $D_n$, $E_n$ (for arbitrary $n \geq 6$), and affine $E_6$, $E_7$ and $E_8$. We show that a natural codimension-$1$ submodule $M$ of the symmetric square of the reflection representation of $W$ has a remarkable canonical basis $\mathcal{B}$ that consists of 2-roots. We prove that, with respect to $\mathcal{B}$, every element of $W$ is represented by a column sign-coherent matrix in the sense of cluster algebras. If $W$ is a finite simply laced Weyl group, each $W$-orbit of 2-roots has a highest element, analogous to the highest root, and we calculate these elements explicitly. We prove that if $W$ is not of affine type, the module $M$ is completely reducible in characteristic zero and each of its nontrivial direct summands is spanned by a $W$-orbit of 2-roots.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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