The Geometric Mean Squared Displacement and the Stokes-Einstein Scaling   in a Supercooled Liquid
  It is proposed that the rate of relaxation in a liquid is better described by the geometric mean of the van Hove distribution function, rather than the standard arithmetic mean used to obtain the mean squared displacement. The difference between the two means is shown to increase significantly with an increase in the non-Gaussian character of the displacement distribution. Preliminary results indicate that the geometric diffusion constant results in a substantial reduction of the deviation from Stokes-Einstein scaling. 
Shibu Saw and Peter Harrowell
cond-mat.soft cond-mat.dis-nn cond-mat.stat-mech