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We introduce a class of affine Deligne--Lusztig varieties that we call of positive Coxeter type. We show that the affine Deligne--Lusztig varieties of positive Coxeter type have a very simple and explicitly described geometric structure.…

Algebraic Geometry · Mathematics 2026-03-04 Felix Schremmer , Ryosuke Shimada , Qingchao Yu

In this paper we discuss the geometry of affine Deligne Lusztig varieties with very special level structure, determining their dimension and connected and irreducible components. As application, we prove the Grothendieck conjecture for…

Algebraic Geometry · Mathematics 2020-12-21 Paul Hamacher

Motivated by the desire to understand the geometry of the basic loci in the reduction of Shimura varieties, we study their "group-theoretic models" -- generalized affine Deligne-Lusztig varieties -- in cases where they have a particularly…

Algebraic Geometry · Mathematics 2020-09-21 Ulrich Görtz , Xuhua He , Sian Nie

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

We prove an explicit formula for the arithmetic intersection number of diagonal cycles on GSpin Rapoport-Zink spaces in the minuscule case. This is a local problem arising from the arithmetic Gan-Gross-Prasad conjecture for orthogonal…

Number Theory · Mathematics 2019-02-20 Chao Li , Yihang Zhu

In this paper we study the geometric structure of affine Deligne-Lusztig varieties for $GL_n$ and $b$ basic. We introduce a new condition on $\lambda$. If this is satisfied, then the corresponding affine Deligne-Lusztig variety is the…

Algebraic Geometry · Mathematics 2022-04-25 Ryosuke Shimada

Affine Deligne-Lusztig varieties are closely related to the special fibre of Newton strata in the reduction of Shimura varieties or of moduli spaces of $G$-shtukas. In almost all cases, they are not quasi-compact. In this note we prove…

Algebraic Geometry · Mathematics 2020-07-14 Paul Hamacher , Eva Viehmann

Affine Deligne-Lusztig varieties are analogues of Deligne-Lusztig varieties in the context of affine flag varieties and affine Grassmannians. They are closely related to moduli spaces of $p$-divisible groups in positive characteristic, and…

Algebraic Geometry · Mathematics 2018-02-08 Ulrich Goertz

We prove the equidimensionality of affine Deligne-Lusztig varieties in mixed characteristic. This verifies a conjecture made by Rapoport and implies that the results of Nie and Zhou-Zhu can be extended to the whole irreducible components of…

Algebraic Geometry · Mathematics 2025-08-14 Yuta Takaya

We initiate the study of affine Deligne-Lusztig varieties with arbitrarily deep level structure for general reductive groups over local fields. We prove that for GLn and its inner forms, Lusztig's semi-infinite Deligne-Lusztig construction…

Algebraic Geometry · Mathematics 2021-01-06 Charlotte Chan , Alexander B. Ivanov

Motivated by the problem of giving an explicit description of the basic locus in the reduction of Shimura varieties, G\"{o}rtz, He and Nie studied the cases where the basic affine Deligne-Lusztig variety, which serves as its group-theoretic…

Algebraic Geometry · Mathematics 2024-02-21 Ryosuke Shimada

Affine Lusztig varieties encode the orbital integrals of Iwahori--Hecke functions and serve as building blocks for the (conjectural) theory of affine character sheaves. We establish a close relationship between affine Lusztig varieties and…

Representation Theory · Mathematics 2024-10-10 Xuhua He

We prove an explicit degree formula for certain unitary Deligne-Lusztig varieties. Combining with an alternative degree formula in terms of Schubert calculus, we deduce several algebraic combinatorial identities which may be of independent…

Algebraic Geometry · Mathematics 2023-01-24 Chao Li

We formulate and prove a local arithmetic Siegel--Weil formula for GSpin Rapoport--Zink spaces, which is a precise identity between the arithmetic intersection numbers of special cycles on GSpin Rapoport--Zink spaces and the derivatives of…

Number Theory · Mathematics 2021-06-30 Chao Li , Wei Zhang

We prove the Kudla--Rapoport conjecture for Kr\"amer models of unitary Rapoport--Zink spaces at ramified places. It is a precise identity between arithmetic intersection numbers of special cycles on Kr\"amer models and modified derived…

Number Theory · Mathematics 2023-07-04 Qiao He , Chao Li , Yousheng Shi , Tonghai Yang

The study of affine Deligne-Lusztig varieties originally arose from arithmetic geometry, but many problems on affine Deligne-Lusztig varieties are purely Lie-theoretic in nature. This survey deals with recent progress on several important…

Algebraic Geometry · Mathematics 2018-07-11 Xuhua He

We give a new proof of the fact that affine Deligne-Lusztig varieties for an algebraic group of adjoint type, associated with superbasic elements, are of finite type. The proof uses a property of the associated Hecke algebra, which we…

Algebraic Geometry · Mathematics 2012-04-12 Alexander Ivanov

We determine the set of connected components of minuscule affine Deligne-Lusztig varieties for special maximal compact subgroups of unramified connected reductive groups. Partial results are also obtained for non-minuscule closed affine…

Algebraic Geometry · Mathematics 2015-09-30 Miaofen Chen , Mark Kisin , Eva Viehmann

This paper concerns the dimensions of certain affine Deligne-Lusztig varieties, both in the affine Grassmannian and in the affine flag manifold. Rapoport conjectured a formula for the dimensions of the varieties X_mu(b) in the affine…

Algebraic Geometry · Mathematics 2007-05-23 Ulrich Goertz , Thomas J. Haines , Robert E. Kottwitz , Daniel C. Reuman

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
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