On K3 Surfaces with Large Complex Structure

We discuss a notion of large complex structure for elliptic K3 surfaces with section inspired by the eight-dimensional F-theory/heterotic duality in string theory. This concept is naturally associated with the Type II Mumford partial compactification of the moduli space of periods for these structures. The paper provides an explicit Hodge-theoretic condition for the complex structure of an elliptic K3 surface with section to be large. We also discuss certain geometrical implications of this large complex structure condition in terms of the Kodaira types of the singular fibers of the elliptic fibration.