Diffuse approximation to the kinetic theory in a Fermi system

We suggest the diffuse approach to the relaxation processes within the kinetic theory for the Wigner distribution function. The diffusion and drift coefficients are evaluated taking into consideration the interparticle collisions on the distorted Fermi surface. Using the finite range interaction, we show that the momentum dependence of the diffuse coefficient D_p(p) has a maximum at Fermi momentum p = p_F whereas the drift coefficient K_p(p) is negative and reaches a minimum at p ≈ p_F. For a cold Fermi system the diffusion coefficient takes the nonzero value which is caused by the relaxation on the distorted Fermi surface at temperature T = 0. The numerical solution of the diffusion equation was performed for the particle-hole excitation in a nucleus with A = 16. The evaluated relaxation time τ_r ≈ 8.3 ⋅ 10^-23s is close to the corresponding result in a nuclear Fermi-liquid obtained within the kinetic theory. (author)