This fascinating volume investigates the structure of eigenvectors and
looks at the number of their sign graphs ("nodal domains"), Perron
components, and graphs with extremal properties with respect to
eigenvectors. The Rayleigh quotient and rearrangement of graphs form the
main methodology. Eigenvectors of graph Laplacians may seem a surprising
topic for a book, but the authors show that there are subtle differences
between the properties of solutions of Schrödinger equations on
manifolds on the one hand, and their discrete analogs on graphs.