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We provide a moduli description of the ramified unitary local model of signature $(n-1,1)$ with arbitrary parahoric level structure, assuming the residue field has characteristic not equal to $2$, thereby confirming a conjecture of…

Algebraic Geometry · Mathematics 2025-05-14 Yu Luo

Local models are schemes which are intended to model the \'etale-local structure of p-adic integral models of Shimura varieties. Pappas and Zhu have recently given a general group-theoretic construction of flat local models with parahoric…

Algebraic Geometry · Mathematics 2015-03-10 Brian Smithling

We construct local models of Shimura varieties and investigate their singularities, with special emphasis on wildly ramified cases. More precisely, with the exception of odd unitary groups in residue characteristic $2$ we construct local…

Algebraic Geometry · Mathematics 2024-12-24 Najmuddin Fakhruddin , Thomas Haines , João Lourenço , Timo Richarz

Local models are certain schemes, defined in terms of linear-algebraic moduli problems, which give \'etale-local neighborhoods of integral models of certain p-adic PEL Shimura varieties defined by Rapoport and Zink. When the group defining…

Algebraic Geometry · Mathematics 2010-09-28 Brian D. Smithling

We consider the local model of a Shimura variety of PEL type, with the unitary similitudes corresponding to a ramified quadratic extension of $\mathbb{Q}_p$ as defining group. We examine the cases where the level structure at $p$ is given…

Algebraic Geometry · Mathematics 2010-05-19 Kai Arzdorf

Local models are schemes, defined in terms of linear-algebraic moduli problems, which give \'etale-local neighborhoods of integral models of certain p-adic PEL Shimura varieties defined by Rapoport and Zink. In the case of a unitary…

Algebraic Geometry · Mathematics 2014-03-19 Brian D. 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

We construct the Bruhat--Tits stratification of the reduced locus of the ramified unitary Rapoport--Zink space of signature $(n-1,1)$, with the level being the stabilizer of a vertex lattice. We develop the local model theory for…

Algebraic Geometry · Mathematics 2026-05-12 Qiao He , Yu Luo , Yousheng Shi

In this paper, we describe a stratification on the reduced special fiber of the basic unramified unitary Rapoport-Zink space of signature $(1,n-1)$ and at arbitrary parahoric level. We prove the smoothness, irreducibility and compute the…

Number Theory · Mathematics 2026-05-28 Joseph Muller

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

Let $G$ be a simple algebraic group over an algebraically closed field $k$. Let $\Gamma$ be a finite group acting on $G$. We classify and compute the local types of $(\Gamma, G)$-bundles on a smooth projective $\Gamma$-curve in terms of the…

Algebraic Geometry · Mathematics 2023-05-24 Chiara Damiolini , Jiuzu Hong

We construct flat integral moduli schemes of PEL type D and the corresponding flat orthogonal Rapoport--Zink spaces with parahoric level structure over a $p$-adic integer ring. The construction relies on proving a conjecture of…

Number Theory · Mathematics 2026-05-15 Jie Yang , Ioannis Zachos , Zhihao Zhao

We construct the Bruhat-Tits stratification of the reduced basic locus of regular ramified unitary Rapoport-Zink spaces of signature $(n\!-\!1,1)$ at vertex-stabilizer level. To study the Bruhat-Tits strata, we introduce strata…

Number Theory · Mathematics 2025-11-11 Ioannis Zachos , Zhihao Zhao

We study the singularities of integral models of Shimura varieties and moduli stacks of shtukas with parahoric level structure. More generally our results apply to the Pappas-Zhu and Levin mixed characteristic parahoric local models, and to…

Algebraic Geometry · Mathematics 2019-10-14 Thomas J. Haines , Timo Richarz

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

In this paper, we study the cohomology of the ramified PEL unitary Rapoport-Zink space of signature $(1,n-1)$ by using the Bruhat-Tits stratification on its special fiber. As such, we apply the same method that we developped for the…

Number Theory · Mathematics 2023-01-02 Joseph Muller

We use a variation of a classical construction of A. Hatcher to construct virtually all stable exotic smooth structures on compact smooth manifold bundles whose fibers have sufficiently large odd dimension (at least twice the base dimension…

K-Theory and Homology · Mathematics 2012-04-10 Sebastian Goette , Kiyoshi Igusa

We use the idea of splitting models to define and study a semi-stable model for unitary Shimura varieties of signature $(n-1,1)$ with maximal parahoric level structure at ramified primes. In this case, the ``naive'' splitting model defined…

Algebraic Geometry · Mathematics 2026-05-29 Qiao He , Yu Luo , Yousheng Shi

In this article, we study local models associated to certain Shimura varieties. In particular, we present a resoultion of their singularities. As a consequence, we are able to determine the alternating semisimple trace of the geometric…

Algebraic Geometry · Mathematics 2007-05-23 Nicole Kraemer

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
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