arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1003.0564math.RThep-thmath-phmath.MP
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双曲Dynkin图、根长和外尔群轨道的分类

Classification of hyperbolic Dynkin diagrams, root lengths and Weyl group orbits

Lisa Carbone, Sjuvon Chung, Leigh Cobbs, Robert McRae, Debajyoti Nandi, Yusra Naqvi, Diego Penta

摘要:

我们给出了Dynkin图(等价于广义Cartan矩阵)可对称化的一个判据。这个判据在Dynkin图上很容易检验。给出了紧双曲型Dynkin图的最大秩为5,而紧双曲型可对称化Dynkin图的最大秩为4的简单证明.基于Kac,Kobayashi-Morita,Li和Saçlioglu的早期分类结果,我们提出了238个秩为3-10的双曲Dynkin图,其中142个是可对称化的。对每一个可对称化的双曲广义Cartan矩阵,我们给出了一个对称化,从而得到了相应根系中实根的不同长度。对于每一个这样的双曲根系我们确定了外尔群在实根上的作用的不相交轨道。由此得出双曲根系实根上不相交的外尔群轨道的最大数目为4。

英文摘要:

We give a criterion for a Dynkin diagram, equivalently a generalized Cartan matrix, to be symmetrizable. This criterion is easily checked on the Dynkin diagram. We obtain a simple proof that the maximal rank of a Dynkin diagram of compact hyperbolic type is 5, while the maximal rank of a symmetrizable Dynkin diagram of compact hyperbolic type is 4. Building on earlier classification results of Kac, Kobayashi-Morita, Li and Saçlioglu, we present the 238 hyperbolic Dynkin diagrams in ranks 3-10, 142 of which are symmetrizable. For each symmetrizable hyperbolic generalized Cartan matrix, we give a symmetrization and hence the distinct lengths of real roots in the corresponding root system. For each such hyperbolic root system we determine the disjoint orbits of the action of the Weyl group on real roots. It follows that the maximal number of disjoint Weyl group orbits on real roots in a hyperbolic root system is 4.

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