On near-polygons and the Coxeter cap in PG(5,3) (Q1580995)

Let \(PG(n,q)\) be the \(n\)-dimensional projective space over the Galois field \(GF(q)\). In the paper under review an upper bound for the cardinality of a set of points in \(PG(n,q)\) with the property that no \(t\) of them are contained in a \((t-2)\)-flat \((n\geq r-2\geq 0)\) is found, and the case of equality is investigated. Also all ovoids and Cameron closed sets of the regular near-hexagon related to the extended ternary Golay code are determined.