On the zero mass limit of tagged particle diffusion in the 1-d   Rayleigh-gas
  We consider the M -> 0 limit for tagged particle diffusion in a 1-dimensional Rayleigh-gas, studied originaly by Sinai and Soloveichik (1986), respectively by Szasz and Toth (1986). In this limit we derive a new type of model for tagged paricle diffusion, with Calogero-Moser-Sutherland (i.e. inverse quadratic) interaction potential between the two central particles. Computer simulations on this new model reproduce exactly the numerical value of the limiting variance obtained by Boldrighini, Frigio and Tognetti (2002). 
Peter Balint (1), Balint Toth (1), Peter Toth (2) ((1) Institute of   Mathematics, Technical University of Budapest, (2) Ren...