Large {0,1,…,t}-cliques in dual polar graphs

We investigate {0,1,…,t}-cliques of generators on dual polar graphs of finite classical polar spaces of rank d. These cliques are also known as Erdős-Ko-Rado sets in polar spaces of generators with pairwise intersections in at most codimension t. Our main result is that we classify all such cliques of maximum size for t≤8d/5−2 if q≥3, and t≤8d/9−2 if q=2. We have the following byproducts.