arXiv subjects

Jingren Chi

Publications and source records attributed to Jingren Chi.

7 recordsLinked to original sources

arXiv2026

Reductive monoids over general base

We develop a theory of affine algebraic monoids over general base schemes whose unit groups are split reductive groups. Our main result is a classification theorem for such objects, generalizing works of Vinberg and Rittatore over a field. As applications, we obtain combinatorial descriptions and normality properties of orbit closures, prove a Steinberg-type theorem on adjoint quotients of reductive monoids over general base schemes, and construct finite type integral models of the Vinberg monoids. A main tool in our construction is Lusztig's theory of modified quantum groups and their canonical bases.

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arXiv2026

An overview of the geometry of Kottwitz-Viehmann varieties

This is an update of an expository article on the geometrization of orbital integrals of spherical Hecke functions on reductive groups over non-archimedean local fields, appeared in Proceedings of ICCM 2019. Compared to the published version, we add a last section on an example in SL3 case.

math.RT↗

arXiv2026

Equivalued affine springer fibers in mixed characteristic

We study Witt-vector affine Springer fibers for tame equi-valued conjugacy classes in tamely ramified groups. Similar to the approach of Goresky-Kottwitz-MacPherson in the equal characteristic setting, we show that they admit pavings by perfections of iterated affine space bundles over smooth Hessenberg varieties. Along the way we prove a version of the Chevalley restriction theorem for the dual of Lie algebras.

math.AG↗

arXiv2025

On the cohomology of simple Shimura varieties with non quasi-split local groups

We study the Scholze test functions for bad reduction of simple Shimura varieties at a prime where the underlying local group is any inner form of a product of Weil restrictions of general linear groups. Using global methods, we prove that these test functions satisfy a vanishing property of their twisted orbital integrals, and we prove that the pseudostabilization base changes of such functions exist (even though the local group need not be quasi-split) and can be expressed in terms of explicit distributions in the stable Bernstein center. We then deduce applications to the stable trace formula and local Hasse-Weil zeta functions for these Shimura varieties.

math.NT↗

arXiv2024

Witt vector affine Springer fibers

We establish dimension formulas for the Witt vector affine Springer fibers associated to a reductive group over a mixed characteristic local field, under the assumption that the group is essentially tamely ramified and the residue characteristic is not bad. Besides the discriminant valuations that show up in classical works on the usual affine Springer fibers, our formula also involves the Artin conductors and the Kottwitz invariants of the relevant conjugacy classes.

math.AG↗

arXiv2018

The geometry of some generalized affine Springer fibers

We study basic geometric properties of some group analogue of affine Springer fibers and compare with the classical Lie algebra affine Springer fibers. The main purpose is to formulate a conjecture that relates the number of irreducible components of such varieties for a reductive group $G$ to certain weight multiplicities defined by the Langlands dual group $\hat{G}$. We prove our conjecture in the case of unramified conjugacy class.

math.AG↗

arXiv2018

Geometry of Kottwitz-Viehmann Varieties

We study basic geometric properties of Kottwitz-Viehmann varieties, which are certain generalizations of affine Springer fibers that encode orbital integrals of spherical Hecke functions. Based on previous work of A. Bouthier and the author, we show that these varieties are equidimensional and give a precise formula for their dimension. Also we give a conjectural description of their number of irreducible components in terms of certain weight multiplicities of the Langlands dual group and we prove the conjecture in the case of unramified conjugacy class.

math.AG↗