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We develop local cohomology techniques to study the finite slope part of the coherent cohomology of Shimura varieties. The local cohomology groups we consider are a generalization of overconvergent modular forms, and they are defined by…

Number Theory · Mathematics 2021-10-22 George Boxer , Vincent Pilloni

We construct exotic Hecke correspondences between the special fibers of different PEL type Shimura varieties, when the local groups are restrictions of scalars of unramified groups. In particular, the local groups themselves are not…

Algebraic Geometry · Mathematics 2026-03-11 Thibaud van den Hove

We prove a conjecture of Broue about the Jordan decomposition of blocks of finite reductive groups. We show that a block of a finite connected reductive group, in non-describing characteristic, is Morita-equivalent to a quasi-isolated block…

Representation Theory · Mathematics 2007-05-23 Cedric Bonnafe , Raphael Rouquier

We extend the work of Pappas-Rapoport-Zhu on twisted affine Grassmannians to wildly ramified, quasi-split, and residually split groups, assuming the maximal torus is induced. This relies on the construction, inspired by Tits, of certain…

Algebraic Geometry · Mathematics 2021-02-04 João Lourenço

We study the supersingular locus of a reduction at an inert prime of the Shimura variety attached to $\mathrm{GU}(2,n-2)$. More concretely, we realize irreducible components of the supersingular locus as closed subschemes of flag schemes…

Number Theory · Mathematics 2025-07-17 Maria Fox , Naoki Imai

We determine the Galois representations inside the $l$-adic cohomology of some unitary Shimura varieties at split places where they admit uniformization by finite products of Drinfeld upper half spaces. Our main results confirm…

Number Theory · Mathematics 2016-11-15 Xu Shen

We construct an endoscopic decomposition for local L-packets associated to irreducible cuspidal Deligne-Lusztig representations. Moreover, the obtained decomposition is compatible with inner twistings.

Representation Theory · Mathematics 2007-05-23 David Kazhdan , Yakov Varshavsky

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 develop a theory of affine flag varieties and of their Schubert varieties for reductive groups over a Laurent power series local field k((t)) with k a perfect field. This can be viewed as a generalization of the theory of affine flag…

Algebraic Geometry · Mathematics 2008-04-24 G. Pappas , M. Rapoport

I employ methods from derived algebraic geometry to give a uniform moduli-theoretic construction of special cycle classes on integral models many Shimura varieties of Hodge type, including unitary, quaternionic, and orthogonal Shimura…

Number Theory · Mathematics 2023-06-05 Keerthi Madapusi

In this paper, we study the affine Deligne--Lusztig variety $X(\mu,b)_K$ and classify all quadruples $(\mathbf{G}, \mu, b, K)$ with $\dim X(\mu, b)_K=0$. This question was first asked by Rapoport in 2005, who also made an explicit…

Algebraic Geometry · Mathematics 2024-02-26 Xuhua He , Sian Nie , Qingchao Yu

Cases of Shimura varieties where the special fibre of a Rapoport-Zink space is simply the union of classical Deligne-Lusztig varieties are known as fully Hodge-Newton decomposable ones, and have been studied with great interest in the past.…

Algebraic Geometry · Mathematics 2025-08-15 Sian Nie , Felix Schremmer , Qingchao Yu

For Shimura varieties of Hodge type, we show that there are natural isomorphisms between locally analytic complete cohomology groups and cohomology groups for flag varieties with coefficient which is given by their perfectoid covers. This…

Number Theory · Mathematics 2025-08-18 Kensuke Aoki

We propose a new stratification of the reduced subschemes of Rapoport-Zink spaces and of affine Deligne-Lusztig varieties that highlights the relation between the geometry of these spaces and the action of the associated automorphism group.…

Algebraic Geometry · Mathematics 2016-09-15 Miaofen Chen , Eva Viehmann

In this paper, we define a family of affinoids in the tubular neighborhoods of CM points in the Lubin-Tate curve with suitable level structures, and compute the reductions of them in the equal characteristic case. By using etale cohomology…

Number Theory · Mathematics 2016-05-02 Takahiro Tsushima

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

We prove a character formula for some closed fine Deligne-Lusztig varieties. We apply it to compute fixed points for fine Deligne-Lusztig varieties arising from the basic loci of Shimura varieties of Coxeter type. As an application, we…

Number Theory · Mathematics 2020-01-22 Xuhua He , Chao Li , Yihang Zhu

This article contributes to the study of the generic part of the cohomology of Shimura varieties. Under a mild restriction of the characteristic of the coefficient field, we prove a torsion vanishing result for Shimura varieties of abelian…

Number Theory · Mathematics 2025-09-16 Xiangqian Yang , Xinwen Zhu

We show that for a variety which admits a quasi-finite period map, finiteness (resp.~non-Zariski-density) of $S$-integral points implies finiteness (resp.~non-Zariski-density) of points over all $\mathbb{Z}$-finitely generated integral…

Algebraic Geometry · Mathematics 2021-05-12 Ariyan Javanpeykar , Daniel Litt

We consider the category of depth $0$ representations of a $p$-adic quasi-split reductive group with coefficients in $\overline{\mathbb{Z}}[\frac{1}{p}]$. We prove that the blocks of this category are in natural bijection with the connected…

Representation Theory · Mathematics 2025-02-10 Jean-François Dat , Thomas Lanard