Baer cone intersections

Abstract

If K is a blocking set of a projective space \( \mathcal{P}\) and P a point not in K, then the projection of K from P onto a hyperplane π of \( \mathcal{P}\) not containing P is a blocking set of π. Projecting a blocking set K of PG(3, q2) from two different points P0, P1 onto a plane π neither containing P0 nor P1, the intersection of the two cones with vertices P0 and P1 and bases the corresponding projections onto π should constitute a big part of the blocking set. Looking for non-trivial blocking sets, the bases contain each a Baer subplane of π. Hence the intersection of the two Baer cones over these Baer subplanes with the vertices P0 and P1 are part of the blocking set K in PG(3, q2). In this article, we describe the intersection configurations of two Baer cones in PG(3, q2).