Article

Designs, Codes and Cryptography

, Volume 65, Issue 1, pp 71-75

Open Access This content is freely available online to anyone, anywhere at any time.

The graph with spectrum 141 240 (−4)10 (−6)9

  • Aart BlokhuisAffiliated withDepartment of Mathematics, Eindhoven University of Technology
  • , Andries E. BrouwerAffiliated withDepartment of Mathematics, Eindhoven University of Technology
  • , Willem H. HaemersAffiliated withDepartment of Econometrics & O.R., Tilburg University Email author 

Abstract

We show that there is a unique graph with spectrum as in the title. It is a subgraph of the McLaughlin graph. The proof uses a strong form of the eigenvalue interlacing theorem to reduce the problem to one about root lattices.

Keywords

Graph spectrum Strongly regular graph Root lattice

Mathematics Subject Classification (2000)

05C50 05E30 05C62