Time-scale invariance of relaxation processes of density fluctuation in slow neutron scattering in liquid cesium

The realization of the idea of time-scale invariance for relaxation processes in liquids has been performed by the memory functions formalism. The best agreement with experimental data for the dynamic structure factor S(k,omega) of liquid cesium near melting point in the range of wave vectors (0.4 A(-1) < or = k < or = 2.55 A(-1)) is found with the assumption of concurrence of relaxation scales for memory functions of third and fourth orders. Spatial dispersion of the first four points in the spectrum of the statistical parameter of non-Markovity epsilon(i)(k,omega) at i=1,2,3,4 has allowed us to reveal the non-Markov nature of collective excitations in liquid cesium, connected with long-range memory effect.