STEADY-STATE NOISES IN DIFFUSION-LIMITED FRACTAL GROWTH

The temporal development of patterns in diffusion-limited aggregation (DLA) growth in cylinder geometry is accompanied by various fluctuating quantities. We give experimental evidence that the fluctuations of the highest growth probability and those of the thickness of the interface and of the distance between the highest site and the average height of deposition, have spectra proportional to 1/f-beta. There are two perhaps three crossovers in the exponent, corresponding to the size of the atoms, the thickness of the interface and the width of the cylinder. Fluctuations of very low frequency are not 1/f-beta. Thus, the basic Gaussian white noise propelling the Brownian motion of the atoms, interacting with the geometry it creates, is transformed into various 1/f-beta noises.