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arXiv 0810.2919math.COmath.RT
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权多重自由表示的权偏序集的性质

Properties of weight posets for weight multiplicity free representations

Dmitri I. Panyushev

摘要:

研究了约化李代数的权多重自由(=wmf)表示$R$的权偏序集.具体来说,我们感兴趣的$\dim R$和相应的权重偏序集,$# E(R)$的哈斯图中的边缘的数量之间的关系。我们计算所有wmf-表示的权偏序集的边数和上覆盖多项式。我们还指出了不同的不可约wmf-表示的权偏序集之间的非平凡同构。我们的主要结果涉及与单李代数的周期分次或Z-分次相关的wmf-表示。对于Z-分次,我们证明了$0< 2dim R-# E(R) < h$,其中$h$是$\mathfrak g$的Coxeter数。对于周期分级,我们证明了$0\le 2dim R-# E(R)$。

英文摘要:

We study weight posets of weight multiplicity free (=wmf) representations $R$ of reductive Lie algebras. Specifically, we are interested in relations between $\dim R$ and the number of edges in the Hasse diagram of the corresponding weight poset, $# E(R)$. We compute the number of edges and upper covering polynomials for the weight posets of all wmf-representations. We also point out non-trivial isomorphisms between weight posets of different irreducible wmf-representations. Our main results concern wmf-representations associated with periodic gradings or Z-gradings of simple Lie algebras. For Z-gradings, we prove that $0< 2dim R-# E(R) < h$, where $h$ is the Coxeter number of $\mathfrak g$. For periodic gradings, we prove that $0\le 2dim R-# E(R)$.

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