Hemisystems of the Hermitian Surface

TL;DR

This paper introduces a novel approach to studying hemisystems of the Hermitian surface using maximal curves, resulting in the construction of hemisystems for primes of a specific form, highlighting their rarity.

Contribution

The paper presents a new method linking maximal curves to hemisystems of the Hermitian surface, producing explicit constructions for primes of the form p=1+16n^2.

Findings

Constructed hemisystems for primes p=1+16n^2

Hemisystems are rare, linked to primes of a special form

Limited known primes with this property, supporting rarity

Abstract

We present a new method for the study of hemisystems of the Hermitian surface $\mathcal{U}_3$ of $PG(3,q^2)$. The basic idea is to represent generator-sets of $\mathcal{U}_3$ by means of a maximal curve naturally embedded in $\mathcal{U}_3$ so that a sufficient condition for the existence of hemisystems may follow from results about maximal curves and their automorphism groups. In this paper we obtain a hemisystem in $\ PG(3,p^2)$ for each $p$ prime of the form $p=1+16n^2$ with an integer $n$. Since the famous Landau's conjecture dating back to 1904 is still to be proved (or disproved), it is unknown whether there exists an infinite sequence of such primes. What is known so far is that just $18$ primes up to $51000$ with this property exist, namely $17,257,401,577, 1297,1601, 3137, 7057,13457,14401,15377,24337,25601,30977,$ $ 32401,33857,41617,50177.$ The scarcity of such primes seems to confirm that hemisystems of $\mathcal{U}_3$ are rare objects.