Relation graphs of an association scheme based on attenuated spaces

The set of subspaces with a given dimension in an attenuated space has a structure of a symmetric association scheme, which is a generalization of both Grassmann schemes and bilinear forms schemes. In this paper, we focus on two families of relation graphs. Their full automorphism groups are completely determined. As a consequence, the classical results of the automorphism groups of Grassmann graphs and bilinear forms graphs are generalized.