Carathéodory hyperbolicity, volume estimates and level structures over function fields

We give a generalization of the nonexistence of level structures as in Nadel (Ann. Math. (2) 129(1):161–178, 1989), Noguchi (Int J Math 2(2):183–194, 1991) and Hwang and To (Math Ann 335(2):363–377, 2006) for quasi-projective manifolds uniformized by strongly Carathéodory hyperbolic complex manifolds. Examples include moduli space of compact Riemann surfaces with a finite number punctures and locally Hermitian symmetric spaces of finite volume. This leads to the nonexistence of a holomorphic map from a Riemann surface of fixed genus into the compactification of such a quasi-projective manifold when the level structure is sufficiently high. To achieve our goal, we have also established some volume estimates for mapping of curves into these manifolds, extending some earlier result of Hwang and To (2006) to a more general setting. A version of Schwarz Lemma applicable to manifolds equipped with nonsmooth complex Finsler metric is also given.