Azimuthally averaged radial profile of the disk potential (given in normalized units) at different evolutionary times sampled every 500 yrs. Some change in the potential is also due to the mass loss through the inner and outer borders of the computational grid. The two bottom plots illustrate the azimuthal variation, computed as , at t = 2500 and t = 4000 yr, respectively. The azimuthal variation is not regular and depends on the evolutionary time.