Strongly regular graphs with parameters (4m4,2m4+m2,m4+m2,m4+m2) exist for all m1

  • Authors:
  • Willem H. Haemers;Qing Xiang

  • Affiliations:
  • Department of Econometrics and O.R., Tilburg University, Tilburg, The Netherlands;Department of Mathematical Sciences, University of Delaware, Newark, DE 19716, USA

  • Venue:
  • European Journal of Combinatorics
  • Year:
  • 2010

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Abstract

Using results on Hadamard difference sets, we construct regular graphical Hadamard matrices of negative type of order 4m^4 for every positive integer m. If m1, such a Hadamard matrix is equivalent to a strongly regular graph with parameters (4m^4,2m^4+m^2,m^4+m^2,m^4+m^2). Strongly regular graphs with these parameters have been called max energy graphs, because they have maximal energy (as defined by Gutman) among all graphs on 4m^4 vertices. For odd m=3 the strongly regular graphs seem to be new.