A phenomenological approach to relaxation in disordered systems

We propose a phenomenological approach to relaxation in disordered systems which is modelled after the well-known percolation behaviour. The approach shows an interesting behaviour of the time correlation function of relevant variables which is characterized by three temporal regimes, an initial exponential decay, a power-law regime and a stretched exponential decay for long times. We give some relevant examples of this behaviour in a wide variety of systems such as gels, microemulsions and glasses.