On triangle-free distance-regular graphs with an eigenvalue multiplicity equal to the valency

Let be a triangle-free distance-regular graph with diameter d 3, valency k 3 and intersection number a2 = 0. Assume has an eigenvalue with multiplicity k. We show that if for d 4 we have a4 = 0, then is 1-homogeneous in the sense of Nomura. In particular, the following infinite family of feasible intersection arrays {2

• Type: Journal
• Year: 2008
• Where: EJC
• Authors: Kris Coolsaet, Aleksandar Jurisic, Jack H. Koolen
• Keywords: EJC 2007, EJC 2008, Feasible Intersection, Information Technology, Number A2, Triangle-free Distance-regular Graph