Complex Networks and Infrastructural Grids

Electric grids, telecommunication networks, railways, healthcare sys- tems, financial circuits, etc. are infrastructures that are critical for func- tioning and the welfare of our countries. Most of such infrastructures have been developed and designed according to engineering paradigms that are staring to become inadequate to cope with their increasing complexity. Much of this complexity is simply due to increased system size: as statis- tical physics teaches us, collection of interacting objects exhibit emergent phenomena (like phase transitions) that goes beyond to the properties of the single objects and have peculiar characteristics in the infinite size limit. Moreover, the increase of interdependencies among the infrastruc- tures (think as an example of the interdependence among communication networks and electric grids) is adding a further element of complexity. Hence, the statistical physics' approach can enlarge the understanding of the fragilities and vulnerabilities of such critical infrastructures. In these chapter we will cover some of the current models of infrastructural grids -- both isolated and coupled -- hinting out the possible and needed development of the field.