The gewirtz graph: An exercise in the theory of graph spectra

Abstract

We prove that there is a unique graph (on 56 vertices) with spectrum 101235(-4)20 and examine its structure. It turns out that, e.g., the Coxeter graph (on 28 vertices) and the Sylvester graph (on 36 vertices) are induced subgraphs. We give descriptions of this graph. © 1993 Academic Press, Inc.