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We prove a conjecture of Pappas and Rapoport about the existence of ''canonical'' integral models of Shimura varieties of Hodge type with quasi-parahoric level structure at a prime $p$. For these integral models, we moreover show…

Number Theory · Mathematics 2026-04-27 Patrick Daniels , Pol van Hoften , Dongryul Kim , Mingjia Zhang

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

Kottwitz conjectured a formula for the (semi-simple) trace of Frobenius on the nearby cycles for the local model of a Shimura variety with Iwahori-type level structure. In this paper, we prove his conjecture in the linear and symplectic…

Algebraic Geometry · Mathematics 2007-05-23 T. Haines , B. C. Ngo

We prove that Shimura varieties admit integral canonical models for sufficiently large primes. In the case of abelian-type Shimura varieties, this recovers work of Kisin-Kottwitz for sufficiently large primes. We also prove the existence of…

Number Theory · Mathematics 2025-02-26 Benjamin Bakker , Ananth N Shankar , Jacob Tsimerman

We consider Shimura varieties associated to a unitary group of signature $(2,n-2)$. We give regular $p$-adic integral models for these varieties over odd primes $p$ which ramify in the imaginary quadratic field with level subgroup at $p$…

Number Theory · Mathematics 2024-09-25 Ioannis Zachos

We investigate the geometry of the special fiber of the integral model of a Shimura variety with parahoric level at a given prime place. To be more precise, we deal with the definition of central leaves in this situation, their local…

Algebraic Geometry · Mathematics 2020-04-13 Jens Hesse

We consider Shimura varieties associated to a unitary group of signature $(n-s,s)$ where $n$ is even. For these varieties, we construct smooth $p$-adic integral models for $s=1$ and regular $p$-adic integral models for $s=2$ and $s=3$ over…

Number Theory · Mathematics 2025-07-18 Ioannis Zachos , Zhihao Zhao

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

In this paper we study the geometry of reduction modulo $p$ of the Kisin-Pappas integral models for certain Shimura varieties of abelian type with parahoric level structure. We give some direct and geometric constructions for the EKOR…

Algebraic Geometry · Mathematics 2020-11-18 Xu Shen , Chia-Fu Yu , Chao Zhang

Local models are schemes defined in terms of linear algebra which can be used to study the local structure of integral models of certain Shimura varieties, with parahoric level structure. We investigate the local models for groups of the…

Algebraic Geometry · Mathematics 2007-05-23 Ulrich Goertz

We compute the connected components of arbitrary parahoric level affine Deligne-Lusztig varieties and local Shimura varieties, thus resolving a folklore conjecture in full generality (even for non-quasisplit groups). We achieve this by…

Number Theory · Mathematics 2025-11-11 Ian Gleason , Dong Gyu Lim , Yujie Xu

This survey article explains the construction of Rapoport-Zink local models and their use in understanding various questions relating to the singularities in the reduction modulo p of certain Shimura varieties with parahoric level structure…

Algebraic Geometry · Mathematics 2007-05-23 Thomas J. Haines

We investigate the bad reduction of certain Shimura varieties (associated to the symplectic group). More precisely, we look at a model of the Shimura variety at a prime p, with parahoric level structure at p. We show that this model is…

Algebraic Geometry · Mathematics 2007-05-23 Ulrich Goertz

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

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 study the special fiber of the integral models for Shimura varieties of Hodge type with parahoric level structure constructed by Kisin and Pappas in [KP]. We show that when the group is residually split, the points in the mod $p$ isogeny…

Number Theory · Mathematics 2020-12-23 Rong Zhou

Local models are schemes defined in linear algebra terms that describe the 'etale local structure of integral models for Shimura varieties and other moduli spaces. We point out that the flatness conjecture of Rapoport-Zink on local models…

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

In \textit{Shimuravariet\"{a}ten und Gerben} \cite{LR87}, Langlands and Rapoport developed the theory of pseudo-motivic Galois gerb and admissible morphisms between Galois gerbs, with a view to formulating a conjectural description of the…

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

We survey the theory of local models of Shimura varieties. In particular, we discuss their definition and illustrate it by examples. We give an overview of the results on their geometry and combinatorics obtained in the last 15 years. We…

Algebraic Geometry · Mathematics 2011-08-30 G. Pappas , M. Rapoport , B. Smithling

We consider Shimura varieties associated to a unitary group of signature $(n-1, 1)$. For these varieties, we construct $p$-adic integral models over odd primes $p$ which ramify in the imaginary quadratic field with level subgroup at $p$…

Number Theory · Mathematics 2025-07-08 Ioannis Zachos , Zhihao Zhao