Structure of noise generated on diffusion fronts

During a diffusion process the diffusion front fluctuates leading to a “geometrical noise”. We predict a 1/ƒ2 noise at high frequency and a 1/ƒ noise at low frequency separated by a crossover ƒ∗. We give here scaling expressions sustained by numerical calculations for the fluctuations and the distribution of events as a function of time and diffusion length. The close relation of this approach with noise in invasion experiments in presence of a gravity field is also pointed out.