Solids in the space of the Veronese surface in even characteristic

Abstract

We classify the orbits of solids in the projective space $\text{PG}(5,q)$, $q$ even, under the setwise stabiliser $K \cong \text{PGL}(3,q)$ of the Veronese surface. For each orbit, we provide an explicit representative $S$ and determine two combinatorial invariants: the point-orbit distribution and the hyperplane-orbit distribution. These invariants characterise the orbits except in two specific cases (in which the orbits are distinguished by their line-orbit distributions). In addition, we determine the stabiliser of $S$ in $K$, thereby obtaining the size of each orbit. As a consequence, we obtain a proof of the classification of pencils of conics in $\text{PG}(2,q)$, $q$ even, which to the best of our knowledge has been heretofore missing in the literature.