On the largest independent sets in the Kneser graph on chambers of PG(4,q)

Abstract

Let ${\Gamma }_4$ be the graph whose vertices are the chambers of the finite projective 4-space $\mathrm{PG}(4,q)$, with two vertices being adjacent if the corresponding chambers are in general position. For $q\ge 749$ we show that $(q^2+q+1)(q^3+2q^2+q+1){(q+1)}^2$ is the independence number of ${\Gamma }_4$ and the geometric structure of the largest independent sets is described.