On the classification of hyperovals

Abstract

A hyperoval in the projective plane $\mathbb{P}^2(\mathbb{F}_q)$ is a set of $q+2$ points no three of which are collinear. Hyperovals have been studied extensively since the 1950s with the ultimate goal of establishing a complete classification. It is well known that hyperovals in $\mathbb{P}^2(\mathbb{F}_q)$ are in one-to-one correspondence to polynomials with certain properties, called o-polynomials of $\mathbb{F}_q$. We classify o-polynomials of $\mathbb{F}_q$ of degree less than $\frac12q^{1/4}$. As a corollary we obtain a complete classification of exceptional o-polynomials, namely polynomials over $\mathbb{F}_q$ that are o-polynomials of infinitely many extensions of $\mathbb{F}_q$.