Abstract
The eigenvalues of a graph are those of its adjacency matrix. Recently, Cioabă, Haemers, Vermette and Wong characterized all connected non-bipartite graphs with all but two eigenvalues equal to 1 or . In this article, we will generalize their result by explicitly determining all connected non-bipartite graphs with all but two eigenvalues in the interval .
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Acknowledgements
The second author would like to thank PNPD–CAPES for the support received during 2014. He is also very grateful to the Department of Production Engineering at CEFET/RJ for the excellent hospitality during the time of his stay in Brazil.
Notes
No potential conflict of interest was reported by the authors.