The lambda invariants at CM points

Tonghai Yang, Hongbo Yin, Peng Yu

In the paper, we show that $\lambda (z_1)-\lambda (z_2)$, $\lambda (z_1)$ and $1-\lambda (z_1)$ are all Borcherds products in $X(2)\times X(2)$. We then use the big CM value formula of Bruinier, Kudla, and…