Irreversibility and the probabilistic treatment of the dynamics of classical particles
L.D. Landau Institute for Theoretical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region, Russian Federation
It is shown that B B Kadomtsev’s idea of small ’external noise’ securing a time-irreversible evolution reduces the justification of statistical physics to a fundamentally new formulation which requires that the dynamics of a multiparticle system be treated by neglecting small acceleration particles. It turns out that this formulation not only leads naturally to irreversible evolution but also suggests a new way of constructing kinetic equations capable of correctly accounting for fluctuations. At the early, small-time, stage of evolution, the original correlations are forgotten and ’post-collisional’ ones form. It is the final portion of the first stage and the formation of the ’post-collisional’ correlations which can be described by a closed form kinetic equation. A relation between Kadomtsev’s external noise idea and Bogolyubov’s derivation of kinetic equations is established, leading to a new physical interpretation of the ’molecular chaos’ hypothesis.