Designs, Codes and Cryptography

, Volume 65, Issue 1–2, pp 71–75

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

  • Aart Blokhuis
  • Andries E. Brouwer
  • Willem H. Haemers
Open Access
Article

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 

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Copyright information

© The Author(s) 2011

Authors and Affiliations

  • Aart Blokhuis
    • 1
  • Andries E. Brouwer
    • 1
  • Willem H. Haemers
    • 2
  1. 1.Department of MathematicsEindhoven University of TechnologyEindhovenThe Netherlands
  2. 2.Department of Econometrics & O.R.Tilburg UniversityTilburgThe Netherlands

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