The spectrum of a graph is the (multi)set of eigenvalues of its adjacency matrix (or Laplacian, depending on what you're interested in). In general, two non-isomorphic graphs might have the same spectrum.
Prompted in part by this discussion on reverse engineering a graph from its spectrumthis discussion on reverse engineering a graph from its spectrum, I was wondering:
Are there interesting classes of graphs for which isospectrality implies isomorphism ?
