Potential Theoretic Hyperbolicity and L² extension. Part I: Stein manifolds

We establish a new generalization of an $L^2$ extension theorem of Ohsawa-Takegoshi type. The improvement in the theorem is that it allows the usual curvature assumptions to be significantly weakened in certain favorable settings. The favorable settings come about, for example, when the underlying structure (e.g., the underlying manifold, or the holomorphic Hermitian line bundle whose sections are being extended) has certain potential theoretic positivity. The simplest case occurs when the underlying manifold supports a function with self-bounded gradient in the sense of McNeal, but there are other cases. We demonstrate the improvement over the usual Ohsawa-Takegoshi-type extension theorems through a number of examples.