Blocking sets from a union of plane curves

Abstract

Motivated by a question of Erdős on blocking sets in a projective plane that intersect every line only a few times, several authors have used unions of algebraic curves to construct such sets in ${\mathbb{P}}^2({\mathbb{F}}_q)$. In this paper, we provide new constructions of blocking sets in ${\mathbb{P}}^2({\mathbb{F}}_q)$ from a union of geometrically irreducible curves of a fixed degree $d$. We also establish lower bounds on the number of such curves required to form a blocking set. Our proofs combine tools from arithmetic geometry and combinatorics.

14 pages