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Singular curves on a K3 surface and linear series on their normalizations

Flaminio Flamini·Andreas Leopold Knutsen·Gianluca Pacienza
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Abstract

In this paper, we study the Brill-Noether theory of the normalizations of singular, irreducible curves on a $K3$ surface. We introduce a {\em singular} Brill-Noether number $ρ_{sing}$ and show that if the Picard group of the K3 surface is ${\mathbb Z} [L]$, there are no $g^r_d$'s on the normalizations of irreducible curves in $|L|$, provided that $ρ_{sing} <0$. We give examples showing the sharpness of this result. We then focus on the case of {\em hyperelliptic normalizations}, and classify linear systems $|L|$ containing irreducible nodal curves with hyperelliptic normalizations, for $ρ_{sing}<0$, without any assumption on its Picard group.

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Flaminio Flamini, Andreas Leopold Knutsen, Gianluca Pacienza. 2006-09-19. Singular curves on a K3 surface and linear series on their normalizations. https://arxiv.org/abs/math/0505266

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