Results of the N-body simulation with , , , and M_i = 10, M_o = 20 M_⊕ are over-plotted on those of 2p20 DZ model. The dark and light colours refer to the N-body and hydrodynamical simulation. To facilitate the comparison, we shifted the time axis for the hydrodynamical simulation such that the t = 0 orbit corresponds to the time at which the planets are just outside of 4:3 resonance.