English

Foliations on Shimura varieties in positive characteristic

Algebraic Geometry 2023-03-13 v3 Number Theory

Abstract

This paper is a continuation of [G-dS1]. We study foliations of two types on Shimura varieties SS in characteristic pp. The first, which we call "tautological foliations", are defined on Hilbert modular varieties, and lift to characteristic 00. The second, the "VV-foliations", are defined on unitary Shimura varieties in characteristic pp only, and generalize the foliations studied by us before, when the CM field in question was quadratic imaginary. We determine when these foliations are pp-closed, and the locus where they are smooth. Where not smooth, we construct a "successive blow up" of our Shimura variety to which they extend as smooth foliations. We discuss some integral varieties of the foliations. We relate the quotient of SS 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 pp, to S.S.

Keywords

Cite

@article{arxiv.2205.00702,
  title  = {Foliations on Shimura varieties in positive characteristic},
  author = {Eyal Z. Goren and Ehud de Shalit},
  journal= {arXiv preprint arXiv:2205.00702},
  year   = {2023}
}

Comments

To appear in Journal of Algebraic Geometry. 1 figure

R2 v1 2026-06-24T11:04:21.980Z