Numerical studies on the phase-space evolution of relative motion of two heavy ions

The two-dimensional Fokker-Planck equation describing the phase-space evolution of the reduced density matrixf(r, v; t) with respect to radial distancer and radial velocityv is numerically solved for various cases of inelastic heavy-ion collisions. A comparison of the exact solution with the global moment approach (GMA) used so far by several authors clearly shows that the GMA is not applicable for deeply inelastic collisions. A local moment approach (LMA) is proposed as an approximate solution to the Fokker-Planck equation.