WAVE-PROPAGATION IN ALMOST-PERIODIC STRUCTURES

The unusual phenomena occurring in the wave propagation in almost-peri odic structures - both classical and quantum are studied in this paper . Focusing our attention on structures with spectral measures in the f amily of disconnected iterated function systems, we describe and chara cterize the concept of ''quantum intermittency''. This theory shows th at the nontrivial renormalization properties of the set of orthogonal polynomials associated with these systems are the origin of such ''int ermittency'', and leads to a new determination of the exponents of the asymptotic growth of the moments of the position operator.