TOWARDS AN UNIVERSAL CLASSIFICATION OF SCALE-INVARIANT PROCESSES

We consider fields which take random values over several decades. Star ting from physical examples, we postulate that scale is not an absolut e quantity. We then establish the equivalence between two existing app roaches based on scale symmetry arguments as general as possible. This yields a classification of log-infinitely divisible laws possibly uni versal. The physical significance of the parameters entering in the cl assification is discussed.