Crossover from Reptation to Rouse dynamics in the Extended   Rubinstein-Duke Model
  The competition between reptation and Rouse Dynamics is incorporated in the Rubinstein-Duke model for polymer motion by extending it with sideways motions, which cross barriers and create or annihilate hernias. Using the Density-Matrix Renormalization-Group Method as solver of the Master Equation, the renewal time and the diffusion coefficient are calculated as function of the length of the chain and the strength of the sideways motion. These new types of moves have a strong and delicate influence on the asymptotic behavior of long polymers. The effects are analyzed as function of the chain length in terms of effective exponents and crossover scaling functions. 
Andrzej Drzewinski, J.M.J. van Leeuwen