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Let $F$ be a totally real field in which $p$ is unramified. We study the Goren-Oort stratification of the special fibers of quaternionic Shimura varieties over a place above $p$. We show that each stratum is a $(\mathbb{P}^1)^N$-bundle over…

Algebraic Geometry · Mathematics 2019-02-20 Yichao Tian , Liang Xiao

We present a general and comprehensive overview of recent developments in the theory of integral models of Shimura varieties of Hodge type. The paper covers the following topics: construction of integral models, their possible moduli…

Number Theory · Mathematics 2008-08-12 Adrian Vasiu

We construct integral models of Shimura varieties of abelian type with parahoric level structure over odd primes. These models are \'etale locally isomorphic to corresponding local models.

Number Theory · Mathematics 2026-04-10 Mark Kisin , Georgios Pappas , Rong Zhou

We study some integral model of P.E.L. Shimura varieties of type A for ramified primes. Precisely, we look at the Pappas-Rapoport model (or splitting model) of some unitary Shimura varieties for which there is ramification in the degree 2…

Algebraic Geometry · Mathematics 2024-01-17 Stéphane Bijakowski , Valentin Hernandez

We define and study the Hodge stratification for the special fiber of Shimura varieties defined with the Pappas-Rapoport condition, in the case of low ramification index ($e \leq 3$). For $e \leq 2$, the Hodge polygon induces a strong…

Number Theory · Mathematics 2022-04-22 Stéphane Bijakowski

The special fiber of the local model of a PEL Shimura variety with Iwahori-type level structure admits a cellular decomposition. The set of strata is in a natural way a finite subset of the affine Weyl group determined by the Shimura data.…

Representation Theory · Mathematics 2007-05-23 T. Haines , B. C. Ngo

We propose a conjectural theory of $p$-integral models of Shimura varieties with level structure at $p$ given by a class of normal subgroups of parahoric subgroups with abelian quotient group. The role of the theory of local models is…

Algebraic Geometry · Mathematics 2026-04-08 Georgios Pappas , Michael Rapoport

The motivation for this paper is the study of arithmetic properties of Shimura varieties, in particular the Newton stratification of the special fiber of a suitable integral model at a prime with parahoric level structure. This is closely…

Algebraic Geometry · Mathematics 2019-05-13 Ulrich Goertz , Xuhua He , Sian Nie

Let $F$ be a real quadratic field in which a fixed prime $p$ is inert, and $E_0$ be an imaginary quadratic field in which $p$ splits; put $E=E_0 F$. Let ${{\rm Sh}}_{1,n-1}$ be the special fiber over $\mathbb{F}_{p^2}$ of the Shimura…

Number Theory · Mathematics 2026-01-21 Zijie Tao

We construct integral models over $p=2$ for some Shimura varieties of abelian type with parahoric level structure, extending the previous work of Kim-Madapusi, Kisin, Pappas, and Zhou. For Shimura varieties of Hodge type, we show that our…

Number Theory · Mathematics 2025-03-27 Jie Yang

In this paper we study the Newton stratification on the reduction of Shimura varieties of PEL type with hyperspecial level structure and the Newton stratification on the deformation space of a Barsotti-Tate group with PEL structure. Our…

Algebraic Geometry · Mathematics 2017-03-10 Paul Hamacher

We give an expository overview over recent results on the global structure and geometry of the Newton stratification of the reduction modulo p of Shimura varieties of Hodge type with hyperspecial level structure. More precisely, we discuss…

Algebraic Geometry · Mathematics 2015-11-11 Eva Viehmann

The Bruhat stratification for Shimura varieties of PEL type is studied. In the Siegel case this stratification is a scheme-theoretic variant of the stratification by the a-number. We show that all Bruhat strata are smooth and determine…

Algebraic Geometry · Mathematics 2013-12-25 Torsten Wedhorn

Let $Y$ be a subvariety contained in a smooth Mumford compactification of an orthogonal Shimura variety $M \subset A_g$, where $A_g$ is the moduli space of principally polarized abelian varieties of dimension $g$ with some level structure,…

Algebraic Geometry · Mathematics 2013-06-12 Stefan Müller-Stach , Kang Zuo

This paper is a contribution to the general problem of giving an explicit description of the basic locus in the reduction modulo $p$ of Shimura varieties. Motivated by \cite{Vollaard-Wedhorn} and \cite{Rapoport-Terstiege-Wilson}, we…

Algebraic Geometry · Mathematics 2013-11-26 Ulrich Goertz , Xuhua He

In this paper we study the slope stratification on the good reduction of the type C family Shimura varieties. We show that there is an open dense subset $U$ of the moduli space such that any point in $U$ can be deformed to a point with a…

Algebraic Geometry · Mathematics 2007-05-23 Chia-Fu Yu

Kisin and Pappas constructed integral models of Hodge-type Shimura varieties with parahoric level structure at $p>2$, such that the formal neighbourhood of a mod~$p$ point can be interpreted as a deformation space of $p$-divisible group…

Algebraic Geometry · Mathematics 2018-05-11 Wansu Kim

We study integral models, so-called Pappas-Rapoport or splitting models, of some PEL Shimura Varieties whose data are ramified at a prime p. We show that except in a specific case, these models are smooth when there is no level at p, and we…

Algebraic Geometry · Mathematics 2020-11-02 Stéphane Bijakowski , Valentin Hernandez

Consider a PEL-Shimura variety associated to a unitary group that splits over an unramified extension of Q_p. Rapoport and Zink have defined a model of the Shimura variety over the ring of integers of the completion of the reflex field at a…

Algebraic Geometry · Mathematics 2009-09-25 U. Goertz

We continue our study of the reduction of PEL Shimura varieties with parahoric level structure at primes p at which the group that defines the Shimura variety ramifies. We describe "good" $p$-adic integral models of these Shimura varieties…

Algebraic Geometry · Mathematics 2007-05-23 G. Pappas , M. Rapoport