CM Value Formula for Orthogonal Shimura Varieties with Applications to Lambda Invariants
Time: Mon, 30 Dec 2019, 15:00-16:00
Place: First conference room at the 1st floor, Jinchunyuan West Building
Speaker: Peng Yu 于鹏 (Morningside Center of Mathematics)
Abstract:
In 1985, Gross and Zagier discovered a beautiful factorization formula for the norm of difference of singular moduli. This has inspired a lot of interesting work, one of which is the study of CM values of automorphic Green functions on orthogonal or unitary Shimura varieties. Now we generalize the definition of CM cycles beyond the ‘small’ and ‘big’ CM cycles and give a uniform formula in general using the idea of regularized theta lifts. Finally, as an application, we are able to give an explicit factorization formula for the norm of λ(½(d₁+d₁½)) - λ(½(d₂+d₂½)) with λ being the modular lambda invariant under the condition (d₁, d₂) = 1. The key observation is that λ(z₁) - λ(z₂) is a Borcherds product on X(2) × X(2).