Detecting Network Communities: a new systematic and efficient algorithm

An efficient and relatively fast algorithm for the detection of communities in complex networks is introduced. The method exploits spectral properties of the graph Laplacian-matrix combined with hierarchical-clustering techniques, and includes a procedure to maximize the ``modularity'' of the output. Its performance is compared with that of other existing methods, as applied to different well-known instances of complex networks with a community-structure: both computer-generated and from the real-world. Our results are in all the tested cases, at least, as good as the best ones obtained with any other methods, and faster in most of the cases than methods providing similar-quality results. This converts the algorithm in a valuable computational tool for detecting and analyzing communities and modular structures in complex networks.