1999/09/14 by Alexander Braverman, Braverman, Alexander, Dennis Gaitsgory +1
Mathematics · #Advanced Algebra and Geometry #Advanced Topics in Algebra #Algebraic Geometry (math.AG) #Algebraic structures and combinatorial models #FOS: Mathematics #Representation Theory (math.RT) #math.AG #math.RT
paper · pdf · doi:10.48550/arxiv.math/9909077
10 pages, LaTeX
openalex publication_date 1999/09/14 · arxiv created 2000/02/25 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Let G be a connected reductive group over \CC and let G\vee be the Langlands dual group. Crystals for G\vee were introduced by Kashiwara as certain ``combinatorial skeletons'' of finite-dimensional representations of G\vee. For every dominant integral weight of G\vee Kashiwara constructed a canonical crystal. Other (independent) constructions of those crystals were given by Lusztig and Littelmann. It was also shown by Kashiwara and Joseph that the above family of crystals is unique if certain reasonable conditions are imposed. The purpose of this paper is to give another (rather simple) construction of these crystals using the geometry of the affine Grassmannian \calGG=G(\calK)/G(\calO) of the group G, where \calK=\CC((t)) is the field of Laurent power series and \calO=\CC[[t]] is the ring of Taylor series. We check that the crystals we construct satisfy the conditions of the uniqueness theorem mentioned above, which shows that our crystals coincide with those constructed in \it loc. cit. It would be interesting to find these isomorphisms directly (cf., however, \citeLus3).