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 that such graphs, if not complete 3-partite, must have lambda < 1.
|Place of Publication||Tilburg|
|Number of pages||14|
|Publication status||Published - 2006|
|Name||Center Discussion Paper|