Blokhuis, A.; Brouwer, A.E.; Haemers, W.H. - Tilburg University, Center for Economic Research - 2006
We give some necessary conditions for a graph to be 3-chromatic in terms of the spectrum of the adjacency matrix.For all known distance-regular graphs it is determined whether they are 3-chromatic.A start is made with the classification of 3-chromatic distance-regular graphs, and it is shown...