NEW UNIVERSAL ASPECTS OF DIFFUSION IN STRONGLY CHAOTIC SYSTEMS

We study some new universal aspects of diffusion in chaotic systems, e specially those having very large Lyapunov coefficients on the chaotic (indecomposable, topologically transitive) component. We do this by d iscretizing the chaotic component on the surface-of-section (SOS) in a (large) number N of simplectically equally big cells (in the sense of equal relative invariant ergodic measure, normalized so that the tota l measure of the chaotic component is unity). By iterating the transit ion of the chaotic orbit through the SOS, where j counts the number of iterations (discrete time) and assuming complete lack of correlation, even between consecutive crossings (which can be justified due to the very large Lyapunov exponents) we show the universal approach of the relative measure of the occupied cells, denoted by rho(j), to the asym ptotic value of unity, in the following way: rho(j) = 1 - (1 - 1/N)(j) , so that in the limit of big N, N --> infinity, we have, for j/N fixe d, the exponential law rho(j) approximate to 1 - exp(-j/N). This analy tic result is verified numerically in a variety of specific systems: f or a plane billiard (Robnik 1983, lambda = 0.375), for a 3D billiard ( Prosen 1997 a = 1/5, b = -12/5), for an ergodic logistic map (tent map ), for a standard map (k = 400) and for the hydrogen atom in a strong magnetic field (epsilon = -0.05) the agreement is almost perfect (exce pt, in the latter two systems, for some long-time deviations on very s mall scales). However, for Henon-Heiles system (E = 1/6), and for the standard map (k = 3) the deviations are noticeable though not very big (only about 1%). We have tested the random number generators (Press e t al 1986), and confirmed that some are almost perfect (ran0 and ran3) , whilst two of them (ran1 and ran2) exhibit big deviations.