About the surjectivity of the Wahl map of nodal curves on K3 surfaces

Abstract

I correct an error in my article arXiv:0911.5474, concerning the non-surjectivity of the Wahl map of nodal curves on K3 surfaces. I prove that a modification of the Wahl map is indeed non-surjective for nodal curves with a low number of nodes, on arbitrary K3 surfaces. Along the way, I also obtain a lower bound of independent interest for the multiple point Seshadri constants of K3 surfaces with cyclic Picard group.