Organizers：
Lin Chen, Will Donovan, Penghui Li, Peng Shan, Changjian Su, Wenbin Yan
Seminar I
Speaker：
Max Gurevich (Technion)
Time：
Fri., 10:00-11:00 am, Oct. 17, 2025
Venue：
B627, Shuangqing Complex Building A
Title:
Weak sphericity, weak Arthur packets, and Springer parameters
Abstract:
Arthur packets are natural combinations of irreducible representations of classical-type p-adic groups that typically arise in an automorphic context. There are ongoing attempts to treat the same notion from a microlocal perspective, that is, through the local character expansions of the packets’ constituents. In joint work with Emile Okada, we highlight the role of weakly spherical Arthur packets for that task, namely those containing a representation admitting invariants under a (not necessarily hyperspecial) maximal compact subgroup. Perhaps surprisingly, weakly spherical representations of symplectic/orthogonal groups turn out to be classified by the Lusztig’s canonical quotients that are attached to adjoint nilpotent orbits. If time permits, I will also discuss a crucial tool enabling such studies: A comparison between the endoscopic theory for p-adic groups and the K-theoretic realization of the Deligne-Langlands correspondence for affine Hecke algebras.
Seminar II
Speaker：
Liang Xiao 肖梁 (PKU)
Time：
Fri., 11:10 am-12:10, Oct. 17, 2025
Venue：
B627, Shuangqing Complex Building A
Title:
Higher Chow group version of theta lifts
Abstract:
In the foundational work of Kudla and Millson, they introduced a version of theta lifts which gives rise to generating series with values in Chow cycles on orthogonal of unitary Shimura varieties. A key ingredient in proving the modularity of this generating series is Borcherds' work on singular theta lifts. In this talk, we explain a framework, which hopes to construct a similar generating series with values in higher Chow groups, in which a (conjectural) version of Borcherds' result on singular theta lifts from Sp4 naturally appears. This is largely motivated by potential applications to Beilinson conjecture. This is an ongoing series of joint works with Haocheng Fan, Wenxuan Qi, Linli Shi, Peihang Wu, and Yichao Zhang.
