Conic linear series and pencils of plane quartics

Abstract

We study linear systems cut out by cones of fixed degree on a smooth complex curve $C\subset {\mathbb{P}}^3$. We develop a systematic study of the families of such systems, considering their limits, their infinitesimal behaviour and some associated geometric structures. As an application, we prove the existence of a non-isotrivial pencil of quartics with only one base point, all whose members are irreducible and whose general member is smooth.

31 pages, revised version. Comments still welcome