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Journal of Algebraic Geometry

Journal of Algebraic Geometry

Online ISSN 1534-7486; Print ISSN 1056-3911

   
 
 

 

Foliations on Shimura varieties in positive characteristic


Authors: Eyal Z. Goren and Ehud de Shalit
Journal: J. Algebraic Geom. 33 (2024), 401-454
DOI: https://doi.org/10.1090/jag/820
Published electronically: September 5, 2023
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Abstract | References | Additional Information

Abstract: This paper is a continuation of a paper by de Shalit and Goren from 2018. We study foliations of two types on Shimura varieties $S$ in characteristic $p$. The first, which we call tautological foliations, are defined on Hilbert modular varieties, and lift to characteristic $0$. The second, the $V$-foliations, are defined on unitary Shimura varieties in characteristic $p$ only, and generalize the foliations studied by us before, when the CM field in question was quadratic imaginary. We determine when these foliations are $p$-closed, and the locus where they are smooth. Where not smooth, we construct a successive blowup of our Shimura variety to which they extend as smooth foliations. We discuss some integral varieties of the foliations. We relate the quotient of $S$ by the foliation to a purely inseparable map from a certain component of another Shimura variety of the same type, with parahoric level structure at $p$, to $S.$


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Additional Information

Eyal Z. Goren
Affiliation: McGill University, Montréal, Québec, Canada
MR Author ID: 623278
Email: eyal.goren@mcgill.ca

Ehud de Shalit
Affiliation: Hebrew University of Jerusalem, Israel
MR Author ID: 221112
Email: ehud.deshalit@mail.huji.ac.il

Received by editor(s): May 2, 2022
Received by editor(s) in revised form: May 22, 2022, and January 1, 2023
Published electronically: September 5, 2023
Additional Notes: The authors’ research was supported by ISF grant 276.17 and NSERC grant 223148.
Article copyright: © Copyright 2023 University Press, Inc.