FRACTAL SPECTRUM OF A QUASI-PERIODICALLY DRIVEN SPIN SYSTEM

We perform a numerical spectral analysis of a quasi-periodically drive n spin-1/2 system, the spectrum of which is singular continuous. We co mpute fractal dimensions of spectral measures and discuss their connec tions with the time behaviour of various dynamical quantities, such as the moments of the distribution of the wavepacket. Our data suggest a close similarity between the information dimension of the spectrum an d the exponent ruling the algebraic growth of the 'entropic width' of wavepackets.