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arXiv math/9912105math.QAmath.AGmath.RT
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几何晶体和单能晶体

Geometric and unipotent crystals

Arkady Berenstein, David Kazhdan

摘要:

本文介绍几何晶体和幂幺晶体,它们是柏原晶体基的代数几何类似物。给定一个约化群G,设I是G的Dynkin图的顶点集,T是G的极大环面。代数簇X上的几何G-晶体的结构由一个有理态射γ:X-->T和一个相容族e_i:G_m \times X-->X,i \in I组成,其中G_m是满足辫子关系的乘法群的有理作用。这样的结构导致W对X的理性作用。相当令人惊讶的是,群W的许多有趣的理性作用都来自几何晶体。此外,在最近的工作中出现在γ-函数的构造中的W的作用的所有已知的例子的表示^LG在A。Braverman和D. Kazhdan来自几何晶体。在(G_m)^l上有许多正几何晶体的例子,即,这些几何晶体的作用量ei和态射γ均由正有理表达式给出。对于每个正几何晶体X,我们将对应于朗兰兹对偶群^LG的柏原晶体联系起来。卢斯蒂格几何晶体的另一个应用是平凡化的构造,它是对任何几何SL_n-晶体的W-等变同构X-->γ^{-1}(e)\times T。单能晶体是正常柏原晶体的几何类似物。它们构成一个严格的幺半范畴。对于任何建立在一个变量X上的幂幺晶体,我们将其与一个几何晶体联系起来。

英文摘要:

In this paper we introduce geometric crystals and unipotent crystals which are algebro-geometric analogues of Kashiwara's crystal bases. Given a reductive group G, let I be the set of vertices of the Dynkin diagram of G and T be the maximal torus of G. The structure of a geometric G-crystal on an algebraic variety X consists of a rational morphism γ:X-->T and a compatible family e_i:G_m\times X-->X, i\in I of rational actions of the multiplicative group G_m satisfying certain braid-like relations. Such a structure induces a rational action of W on X. Quite surprisingly, many interesting rational actions of the group W come from geometric crystals. Also all the known examples of the action of W which appear in the construction of gamma-functions for the representations of ^LG in the recent work by A. Braverman and D. Kazhdan come from geometric crystals. There are many examples of positive geometric crystals on (G_m)^l, i.e., those geometric crystals for which the actions e_i and the morphism γare given by positive rational expressions. To each positive geometric crystal X we associate a Kashiwara's crystal corresponding to the Langlands dual group ^LG. An emergence of ^LG in the "crystal world" was observed earlier by G. Lusztig. Another application of geometric crystals is a construction of trivialization which is an W-equivariant isomorhism X-->γ^{-1}(e) \times T for any geometric SL_n-crystal. Unipotent crystals are geometric analogues of normal Kashiwara crystals. They form a strict monoidal category. To any unipotent crystal built on a variety X we associate a certain gometric crystal.

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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