Universality in complex systems

Among complex, interacting systems built up from: particles, galaxies, animals, cars, money, web nodes ... etc. scaling universality classes may appear determined solely by the collective behavior.
Example at critical phase transitions, where the correlation length diverges.
In equilibrium systems these classes are well understood: standard classes; role of symmetries, dimensions, boundary conds. are discovered)

Among complex, interacting systems built up from: particles, galaxies, animals, cars, money, web nodes ... etc. scaling universality classes may appear determined solely by the collective behavior.