Speaker: Dr. Shan Yi (University of Toronto)

Title: Rationality of quaternionic Eisenstein series on U(2,n)

Time: 14:00-15:00  May 15, 2026 (Friday)

Place: MCM110

Abstract: The Eisenstein series form an important family of automorphic forms, and in many cases of holomorphic modular forms, their Fourier coefficients are known to be rational. Recently, a theory on the Fourier expansion of quaternionic modular forms was developed by Pollack for quaternionic exceptional groups, and by Hilado-McGlade-Yan for rank two unitary groups U(2,n).

In this talk, we focus on the even unitary groups U(2,n) that are quasi-split over all finite places. We will present an explicit Fourier expansion for the quaternionic Heisenberg Eisenstein series of weight l>n+1 on U(2,n). As a consequence, this Fourier expansion is rational in a certain sense and the Fourier coefficients have bounded denominators. This talk is based on joint work with Henry H. Kim.