On log--normal distribution on a comb structure
  We study specific properties of particles transport by exploring an exact solvable model, a so-called comb structure, where diffusive transport of particles leads to subdiffusion. A performance of L\'evy -- like process enriches this transport phenomenon. It is shown that an inhomogeneous convection flow, as a realization of the L\'evy--like process, leads to superdiffusion of particles on the comb structure. A frontier case of superdiffusion that corresponds to the exponentially fast transport is studied and the log--normal distribution is obtained for this case. 
E. Baskin and A. Iomin