Graph energy
In mathematics, the energy of a graph is the sum of the absolute values of the eigenvalues of the adjacency matrix of the graph. This quantity is studied in the context of graph theory">Graph (discrete mathematics)">graph theory.
More precisely, let G be a graph with n vertices. It is assumed that G is a simple graph, that is, it does not contain loops or parallel edges. Let A be the adjacency matrix of G and let,, be the eigenvalues of A. Then the energy of the graph is defined as: