Gewirtz Graph: An Exercise in the Theory of Graph Spectra

摘要

It is proven that there is a unique graph (on 56 vertices) with spectrum 10(sup1) 2(sup 35) (-4)(sup 20), and its structure is examined. It turns out that e.g. the Coxeter graph (on 28 vertices) and the Sylvester graph (on 36 vertices) are induced subgraphs. Several descriptions of the graph are given.