Strata Hasse invariants, Hecke algebras and Galois representations

Wushi Goldring; Jean-Stefan Koskivirta

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arXiv · 1507.05032

Strata Hasse invariants, Hecke algebras and Galois representations

Wushi Goldring·Jean-Stefan Koskivirta

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Abstract

We construct group-theoretical generalizations of the Hasse invariant on strata closures of the stacks $G$-Zip$^{\mu}$. Restricting to zip data of Hodge type, we obtain a group-theoretical Hasse invariant on every Ekedahl-Oort stratum closure of a general Hodge-type Shimura variety. A key tool is the construction of a stack of zip flags $G$-ZipFlag$^\mu$, fibered in flag varieties over $G$-Zip$^{\mu}$. It provides a simultaneous generalization of the "classical case" homogeneous complex manifolds studied by Griffiths-Schmid and the "flag space" for Siegel varieties studied by Ekedahl-van der Geer. Four applications are obtained: (1) Pseudo-representations are attached to the coherent cohomology of Hodge-type Shimura varieties modulo a prime power. (2) Galois representations are associated to many automorphic representations with non-degenerate limit of discrete series archimedean component. (3) It is shown that all Ekedahl-Oort strata in the minimal compactification of a Hodge-type Shimura variety are affine, thereby proving a conjecture of Oort. (4) Part of Serre's letter to Tate on mod $p$ modular forms is generalized to general Hodge-type Shimura varieties.

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Wushi Goldring, Jean-Stefan Koskivirta. 2015-07-17. Strata Hasse invariants, Hecke algebras and Galois representations. https://arxiv.org/abs/1507.05032

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