The energy of a graph
نویسندگان
چکیده
The energy, E(G), of a simple graph G is defined to be the sum of the absolute values of the eigen values of G. If G is a k-regular graph on n vertices,then E(G) k+√k(n− 1)(n− k)= B2 and this bound is sharp. It is shown that for each > 0, there exist infinitely many n for each of which there exists a k-regular graph G of order n with k < n− 1 and B2 < . Two graphs with the same number of vertices are equienergetic if they have the same energy. We show that for any positive integer n 3, there exist two equienergetic graphs of order 4n that are not cospectral. © 2004 Elsevier Inc. All rights reserved. AMS classification: 05C50
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