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arXiv 1106.0347math.RT
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流代数的BGG互易性

BGG reciprocity for current algebras

Matthew Bennett, Vyjayanthi Chari, Nathan Manning

摘要:

本文研究当前代数$\lie g\otimes\bc[t]$的有限维分次片的分次表示范畴$\cal I_{\gr}$,其中$\lie g$是简单李代数.这一范畴与$\lie g$的模范畴$\cal O$有许多相似之处,在本文中,我们提出并研究了著名的BGG对偶的一个类似物。我们回顾了$\cal I_{\gr}$中的投影和简单对象的定义,这些对象由主导积分权重索引。韦尔马模的作用是由一个称为全局外尔模的模族来扮演的。证明了当$\lie g$是$\lie{sl}_2$型时,其投射模允许一个标志,其中连续的同元是全局Weyl模的有限直和.一个特定的外尔模在标志中出现的重数由一个紧密相关的模族的Jordan-Holder级数的重数决定,称为局部外尔模。我们猜想这个结果对任意单李代数都成立。我们还证明了一些组合产品-和身份涉及Kostka多项式出现的后果,我们的定理。

英文摘要:

We study the category $\cal I_{\gr}$ of graded representations with finite--dimensional graded pieces for the current algebra $\lie g\otimes\bc[t]$ where $\lie g$ is a simple Lie algebra. This category has many similarities with the category $\cal O$ of modules for $\lie g$ and in this paper, we formulate and study an analogue of the famous BGG duality. We recall the definition of the projective and simple objects in $\cal I_{\gr}$ which are indexed by dominant integral weights. The role of the Verma modules is played by a family of modules called the global Weyl modules. We show that in the case when $\lie g$ is of type $\lie{sl}_2$, the projective module admits a flag in which the successive quotients are finite direct sums of global Weyl modules. The multiplicity with which a particular Weyl module occurs in the flag is determined by the multiplicity of a Jordan--Holder series for a closely associated family of modules, called the local Weyl modules. We conjecture that the result remains true for arbitrary simple Lie algebras. We also prove some combinatorial product--sum identities involving Kostka polynomials which arise as a consequence of our theorem.

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