publications

2023

1. Nonemptiness criterion of affine Deligne-Lusztig varieties

   Dong Gyu Lim

   2023

   Abs arXiv

   Affine Deligne-Lusztig varieties with various level structures show up in the study of Shimura varieties and moduli spaces of shtukas. Among is the Iwahori level structure which is the most refined one. We study the nonemptiness problem of single affine Deligne-Lusztig varieties at Iwahori level in the basic case. Under a genericity condition (the “shrunken Weyl chambers” condition), an explicit criterion is known. However, no explicit criterion has been available without the condition even conjecturally. We conjecture a new criterion in full generality, and prove it except for finitely many cases. As an application, the nonemptiness problem in some non-basic cases and a new conjectural dimension formula are discussed.

2. Hodge-Newton indecomposability and a combinatorial identity

   Dong Gyu Lim

   2023

   Abs arXiv

   We present a simple alternative viewpoint on Hodge-Newton indecomposability, illustrating its explanatory value through a uniform proof of a combinatorial identity arising from affine Deligne-Lusztig varieties with finite Coxeter part.

2026

1. The connected components of affine Deligne-Lusztig varieties

   Ian Gleason, Dong Gyu Lim, and Yujie Xu

   Inventiones Mathematicae 2026

   Abs arXiv Journal

   We compute the connected components of arbitrary parahoric level affine Deligne–Lusztig varieties and local Shimura varieties, thus resolving a folklore conjecture raised in (He in Some results on affine Deligne–Lusztig varieties. YouTube video, 2018; Zhou in Duke Math. J. 169(15):2937–3031, 2020) in full generality (even for non-quasisplit groups). We achieve this by relating them to the connected components of infinite level moduli spaces of p-adic shtukas, where we use v-sheaf-theoretic techniques such as the specialization map of kimberlites. Along the way, we give a p-adic Hodge-theoretic characterization of HN-irreducibility. As applications, we obtain many results on the geometry of integral models of Shimura varieties of Hodge type at arbitrary stabilizer-parahoric levels. In particular, we deduce new CM lifting results on integral models of Shimura varieties for quasisplit groups at parahoric levels that arise as stabilizer Bruhat–Tits group schemes.