Dynamics of heterogeneous hard spheres in a file

Normal dynamics in a quasi-one-dimensional channel of length L (\to\infty) of N hard spheres are analyzed. The spheres are heterogeneous: each has a diffusion coefficient D that is drawn from a probability density function (PDF), W D^(-{\gamma}), for small D, where 0\leq{\gamma}<1. The initial spheres' density {\rho} is non-uniform and scales with the distance (from the origin) l as, {\rho} l^(-a), 0\leqa\leq1. An approximation for the N-particle PDF for this problem is derived. From this solution, scaling law analysis and numerical simulations, we show here that the mean square displacement for a particle in such a system obeys, <r^2>~t^(1-{\gamma})/(2c-{\gamma}), where c=1/(1+a). The PDF of the tagged particle is Gaussian in position. Generalizations of these results are considered.