The twisted Grassmann graph is the block graph of a design

Abstract

In this note, we show that the twisted Grassmann graph constructed by van Dam and Koolen is the block graph of the design constructed by Jungnickel and Tonchev. We also show that the full automorphism group of the design is isomorphic to the full automorphism group of the twisted Grassmann graph.

5 pages. A section on the automorphism group has been added