The known maximal partial ovoids of size $q^2-1$ of Q(4,q)

Abstract

We present a description of maximal partial ovoids of size $q^2-1$ of the parabolic quadric $\q(4,q)$ as sharply transitive subsets of $\SL(2,q)$ and show their connection with spread sets. This representation leads to an elegant explicit description of all known examples. We also give an alternative representation of these examples which is related to root systems.

arXiv comment15 pages, revised version (v2 on arxiv is just a update of another paper, applied on this paper, clearly a mistake...)