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arXiv · 1809.08464

Smoothness of Schubert varieties in twisted affine Grassmannians

Thomas J. Haines·Timo Richarz
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Abstract

We give a complete list of smooth and rationally smooth normalized Schubert varieties in the twisted affine Grassmannian associated with a tamely ramified group and a special vertex of its Bruhat-Tits building. The particular case of the quasi-minuscule Schubert variety in the quasi-split but non-split form of ${\rm Spin}_8$ ("ramified triality") provides an input needed in the article by He-Pappas-Rapoport classifying Shimura varieties with good or semi-stable reduction.

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Thomas J. Haines, Timo Richarz. 2018-09-22. Smoothness of Schubert varieties in twisted affine Grassmannians. https://doi.org/10.1215/00127094-2020-0025

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