The Colin de Verdiere parameter, excluded minors, and the spectral radius

In this paper we characterize graphs which maximize the spectral radius of their adjacency matrix over all graphs of Colin de Verdiere parameter at most m. We also characterize graphs of maximum spectral radius with no H as a minor when H is either K-r or K-s,K-t. Interestingly, the extremal graphs match those which maximize the number of edges over all graphs with no H as a minor when r and s are small, but not when they are larger. (C) 2019 Elsevier Inc. All rights reserved.