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arXiv · 1910.03377

Perverse $\mathbb{F}_p$-sheaves on the affine Grassmannian

Robert Cass
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Abstract

For a reductive group over an algebraically closed field of characteristic $p > 0$ we construct the abelian category of perverse $\mathbb{F}_p$-sheaves on the affine Grassmannian that are equivariant with respect to the action of the positive loop group. We show this is a symmetric monoidal category, and then we apply a Tannakian formalism to show this category is equivalent to the category of representations of a certain affine monoid scheme. We also show that our work provides a geometrization of the inverse of the mod $p$ Satake isomorphism. Along the way we prove that affine Schubert varieties are globally $F$-regular and we apply Frobenius splitting techniques to the theory of perverse $\mathbb{F}_p$-sheaves.

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Robert Cass. 2019-10-08. Perverse $\mathbb{F}_p$-sheaves on the affine Grassmannian. https://arxiv.org/abs/1910.03377

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