Linear system of geometrically irreducible plane cubics over finite fields

Abstract

We examine the maximum dimension of a linear system of plane cubic curves whose ${\mathbb{F}}_q$-members are all geometrically irreducible. Computational evidence suggests that such a system has a maximum (projective) dimension of $3$. As a step towards the conjecture, we prove that there exists a $3$-dimensional linear system $\mathcal{L}$ with at most one geometrically reducible ${\mathbb{F}}_q$-member.

6 pages