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In the paper four stratifications in the reduction modulo $p$ of a general Shimura variety are studied: the Newton stratification, the Kottwitz-Rapoport stratification, the Ekedahl-Oort stratification and the Ekedahl-Kottwitz-Oort-Rapoport…

Algebraic Geometry · Mathematics 2015-09-28 Xuhua He , Michael Rapoport

We construct projective toroidal compactifications for integral models of Shimura varieties of Hodge type. We also construct integral models of the minimal (Satake-Baily-Borel) compactification. Our results essentially reduce the problem to…

Number Theory · Mathematics 2018-03-13 Keerthi Madapusi Pera

We construct canonical extensions of $p$-adic shtukas on integral models of toroidal compactifications of abelian-type Shimura varieties with quasi-parahoric levels at any prime number $p$. More precisely, we define the notion of a log…

Number Theory · Mathematics 2026-05-29 Shengkai Mao , Peihang Wu

Let $G$ be a finite permutation group on $\Omega.$ An ordered sequence $(\omega_1,\dots, \omega_t)$ of elements of $\Omega$ is an irredundant base for $G$ if the pointwise stabilizer is trivial and no point is fixed by the stabilizer of its…

Group Theory · Mathematics 2022-12-27 Andrea Lucchini , Dmitry Malinin

We construct canonical Hasse invariants for arbitrary Shimura varieties of Hodge type for the mu-ordinary locus.

Algebraic Geometry · Mathematics 2018-01-19 Jean-Stefan Koskivirta , Torsten Wedhorn

This is the second in a sequence of articles, in which we explore moduli stacks of global G-shtukas, the function field analogs for Shimura varieties. Here G is a flat affine group scheme of finite type over a smooth projective curve C over…

Number Theory · Mathematics 2019-03-19 Esmail M. Arasteh Rad , Urs Hartl

In this paper, we consider the geometric special fibers of local models of Shimura varieties and of moduli of $\bG$-Shtukas with parahoric level structure. We investigate two problems with respect to the irreducibility of local models.…

Algebraic Geometry · Mathematics 2024-12-24 Xuhua He , Qingchao Yu

We establish the Iwasawa main conjecture for semi-stable abelian varieties over a function field of characteristic $p$ under certain restrictive assumptions. Namely we consider $p$-torsion free $p$-adic Lie extensions of the base field…

Number Theory · Mathematics 2019-01-11 David Vauclair , Fabien Trihan

Let $K_\infty/K$ be a uniform $p$-adic Lie extension. We compare several arithmetic invariants of Iwasawa modules of ideal class groups on the one side and fine Selmer groups of abelian varieties on the other side. If $K_\infty$ contains…

Number Theory · Mathematics 2024-09-24 Sören Kleine , Katharina Müller

We study the rigid cohomology of the ordinary locus in some compact PEL Shimura varieties of type C with values in automorphic local systems and use it to prove a small slope criterion for classicality of overconvergent Hecke eigenforms.…

Number Theory · Mathematics 2013-01-22 Christian Johansson

In the 1960's Igusa determined the graded ring of Siegel modular forms of genus two. He used theta series to construct $\chi_{5}$, the cusp form of lowest weight for the group $\operatorname{Sp}(2;Z)$. In 2010 Gritsenko found three towers…

Number Theory · Mathematics 2018-10-02 Martin Woitalla

This paper is a continuation of [G-dS1]. 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…

Algebraic Geometry · Mathematics 2023-03-13 Eyal Z. Goren , Ehud de Shalit

We compute the level groups associated with mixed Shimura varieties that appear at the boundaries of compactifications of Shimura varieties and show that the boundaries of minimal compactifications of Pappas-Rapoport integral models are…

Number Theory · Mathematics 2025-04-22 Shengkai Mao

We study the image of $\ell$-adic representations attached to subvarieties of Shimura varieties $Sh_K(G,X)$ that are not contained in a smaller Shimura subvariety and have no isotrivial components. We show that, for $\ell$ large enough…

Algebraic Geometry · Mathematics 2019-05-23 Gregorio Baldi

In this paper, we compute the cohomology sheaves of the $\ell$-adic nearby cycles on the local model of the PEL $\mathrm{GU}(n-1,1)$ Shimura variety over a ramified prime, with level given by the stabilizer of a self-dual lattice. This…

Number Theory · Mathematics 2026-05-21 Joseph Muller

We establish basic results on p-adic shtukas and apply them to the theory of local and global Shimura varieties, and on their interrelation. We construct canonical integral models for (local, and global) Shimura varieties of Hodge type with…

Number Theory · Mathematics 2023-10-27 Georgios Pappas , Michael Rapoport

For a Shimura variety of Hodge type with hyperspecial level at a prime $p$, the Newton stratification on its special fiber at $p$ is a stratification defined in terms of the isomorphism class of the Dieudonne module of parameterized abelian…

Number Theory · Mathematics 2016-03-16 Dong Uk Lee

I construct a generalisation of Mantovan's almost product structure to Shimura varieties of Hodge type with hyperspecial level structure at $p$ and deduce that the perfection of the Newton strata are pro-\'etale locally isomorphic to the…

Algebraic Geometry · Mathematics 2018-10-29 Paul Hamacher

Consider all moduli points corresponding with polarized abelian varieties in characteristic p such that the associated quasi-polarized p-divisible group is geometrically isomorphic with a given one. This defines a subset C of the moduli…

Algebraic Geometry · Mathematics 2007-05-23 Frans Oort

In this paper, we study the basic locus in the fiber at $p$ of a certain unitary Shimura variety with a certain parahoric level structure. The basic locus $\widehat{\mathcal{M}^{ss}}$ is uniformized by a formal scheme $\mathcal{N}$ which is…

Number Theory · Mathematics 2018-07-27 Sungyoon Cho