A COMPARISON BETWEEN COLLISIONAL DYNAMICS AND BROWNIAN DYNAMICS

This paper presents an analytical investigation for the velocity relax ation of a test particle coupled to a heat bath by two different mecha nisms: the Brownian dynamics (ED) and the collisional dynamics (CD). R elation between the parameters of the methods is established. The velo city relaxation spectrum induced by the coupling in the CD method is s hown to be different from the one in the ED method. The difference bet ween the spectra disappears in the limit gamma --> O, where gamma is a mass ratio of the bath atoms and the test particle.