  In the paper, we study fluctuations over several ensembles of maximum-entropy
random networks. We derive several fluctuation-dissipation relations
characterizing susceptibilities of different networks to changes in external
fields. In the case of networks with a given degree sequence, we argue that the
scale-free topologies of real-world networks may arise as a result of
self-organization of real systems into sparse structures with low
susceptibility to random external perturbations. We also show that the
ensembles of networks with noninteracting links (both uncorrelated and with
two-point correlations) are equivalent to random networks with hidden
variables.
