扭曲仿射 Grassmann 丛中 Schubert 簇的光滑性
代数几何
2020-12-23 v4 表示论
摘要
我们给出了与驯分歧群及其 Bruhat-Tits 建筑的特殊顶点相关联的扭曲仿射 Grassmann 丛中光滑且有理光滑的规范化 Schubert 簇的完整列表。在 的拟分裂但非分裂形式（“分歧三重性”）中拟极小 Schubert 簇的特殊情形，提供了 He-Pappas-Rapoport 分类具有良好或半稳定约化的 Shimura 簇的文章所需的输入。
引用
@article{arxiv.1809.08464,
title = {Smoothness of Schubert varieties in twisted affine Grassmannians},
author = {Thomas J. Haines and Timo Richarz},
journal= {arXiv preprint arXiv:1809.08464},
year = {2020}
}
备注
24 pages. Minor correction: certain lattices termed almost selfdual in the previous version are now correctly termed almost modular. The article has been recast to apply to normalized Schubert varieties, to account for the existence of non-normal Schubert varieties in small positive characteristics. A new Proposition 2.1 and a new proof of Proposition 2.2 have been given. Accepted version