new bounds for laplacian energy

Introduction/purpose: the laplacian energy (le) is the sum of absolute values of the terms μi-2m/n, where μi, i=1,2,…,n, are the eigenvalues of the laplacian matrix of the graph g with n vertices and m edges. the basic results of the theory of le are outlined, and some new obtained. methods: spectral theory of laplacian matrices is applied. results: a new class of lower bounds for le is derived. conclusion: the paper contributes to the laplacian spectral theory and tp the theory of graph energies.