Open Access
Article

Designs, Codes and Cryptography

, Volume 65, Issue 1, pp 71-75

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

Authors

  • Aart Blokhuis
    • Department of MathematicsEindhoven University of Technology
  • Andries E. Brouwer
    • Department of MathematicsEindhoven University of Technology
  • Willem H. Haemers
    • Department of Econometrics & O.R.Tilburg University

DOI: 10.1007/s10623-011-9529-6

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

Open Access

This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

Copyright information

© The Author(s) 2011