SPATIALLY CHAOTIC CONFIGURATIONS AND FUNCTIONAL-EQUATIONS WITH RESCALING

The functional equation y(qt)=1/4g[y(t+1)+y(t-1)+2y(t)] (0 < q < 1) t epsilon R is associated with the appearance of spatially chaotic struc tures in amorphous (glassy) materials. Continuous compactly supported solutions of the above equation are of special interest. We shall show that there are no such solutions for 0 < q < 1, whereas such a soluti on exists for almost all 1/2 < q < 1. The words 'for almost all q' in the previous sentence cannot be omitted. There are exceptional values of q in the interval [1/2, 1] for which there are no integrable soluti ons. For example, q = (root 5 - 1)/2 approximate to 0.618, which is th e reciprocal of the 'golden ratio' is such an exceptional value. More generally, if I is any Pisot-Vijayaraghavan number, or any Salem numbe r, then q = lambda(-1) is an exceptional value.