An application of Hoffman graphs for spectral characterizations of graphs

Qianqian Yang, Aida Abiad Monge, Jack H. Koolen*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

In this paper, we present that the 2-clique extension of the (t + 1) x (t + 1)-grid is determined by its spectrum if t is large enough. By applying results of Gavrilyuk and Koolen, this implies that the Grassmann graph J(2)(2D, D) is determined by its intersection array as a distance-regular graph if D is large enough. The main tool we are using is Hoffman graphs.
Original languageEnglish
Article numberP1.12
Number of pages24
JournalElectronic Journal of Combinatorics
Volume24
Issue number1
DOIs
Publication statusPublished - 20 Jan 2017

Keywords

  • Hoffman graph
  • graph eigenvalue
  • interlacing
  • walk-regular
  • spectral characterizations
  • SMALLEST EIGENVALUE

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