CORRELATED MOTION OF 2 PARTICLES IN A DENSE FLUID OF HARD-RODS

An exact equation describing the stochastic motion of a droplet of nei ghbouring equal mass hard points with velocities +/- c, immerzed in a hard point fluid, is derived, The derivation generalizes Resibois' ide a originally applied to the study of self-diffusion. The explicit solu tion for a two-particle droplet is obtained, showing a rapid relaxatio n of the interparticle distance to the Poisson distribution, superpose d on a slow diffusive motion of the centre of mass of the two particle s. An approximate description of the dynamics of N-particle droplets ( N > 2) is proposed.