Low degree rational curves on quasi-polarized K3 surfaces

Abstract

We prove that there are at most $(24-r_0)$ irreducible rational curves of positive low-degree on high-degree models of K3 surfaces with at most Du Val singularities, where $r_0$ is the number of exceptional divisors on the minimal resolution. We also provide several existence results in the above setting (i.e. for rational curves on quasi-polarized K3 surfaces), which imply that for many values of $r_0$ our bound cannot be improved.