Sven Bilke and Carsten Peterson Topological Properties of Citation and Metabolic Networks Physical Review E 64, 036106 (2001) Abstract: Topological properties of "scale-free" networks are investigated by determining their spectral dimensions dS, which reflect a diffusion process in the corresponding graphs. Data bases for citation networks and metabolic networks together with simulation results from the growing network model are probed. For completeness and comparisons lattice, random, small-world models are also investigated. We find that dS is around three for citation and metabolic networks, which is significantly different from the growing network model, for which dS is approximately 7.5. This signals a substantial difference in network topology despite the observed similarities in vertex order distributions. In addition, the diffusion analysis indicates that whereas the citation networks are tree-like in structure, the metabolic networks contain many loops. LU TP 01-09