Symmetric differentials and jets extension of $L^2$ holomorphic functions II: Explicit form
Seungjae Lee, Aeryeong Seo
TL;DR
The paper delivers an explicit integral formula for the map $\Phi$ that associates symmetric differentials on a ball quotient to weighted $L^2$ holomorphic functions on the corresponding ball bundle. The key tool is the gradient of $\varphi_{z,w}$, built from the Bergman kernel, which yields a higher-dimensional analogue of Adachi's cross-ratio. This explicit form enables concrete representations of Poincaré series, clarifies the relation between Bergman kernels on $\Sigma$ and weighted kernels on $\Omega$, and extends naturally to totally geodesic embeddings, enhancing the analytic and geometric understanding of the $L^2$-jet extension problem. The results have potential impacts on the study of automorphic forms, holomorphic sections on ball quotients, and geometric embeddings into higher-dimensional balls.
Abstract
For a symmetric differential on the compact quotient $Σ= \mathbb{B}^n / Γ$ of the complex unit ball $\mathbb{B}^n \subset \mathbb{C}^n$ by a discrete subgroup $Γ\subset \mathrm{Aut}(\mathbb{B}^n)$, there exists a corresponding weighted $L^2$-holomorphic function on $(\mathbb{B}^n \times \mathbb{B}^n)/Γ$, where $Γ$ acts diagonally on $\mathbb{B}^n \times \mathbb{B}^n$. In this paper, we give an explicit description of this correspondence and derive several applications based on its explicit form.
