INERTIAL AND DISSIPATIVE PROPERTIES OF SURFACE EXCITATIONS IN A FERMI-LIQUID

The kinetic properties of surface excitations in a Fermi liquid are co nsidered, using the Vlasov equation for a Fermi system with a moving f ree surface. Expressions for the mass and friction coefficients for th e collective variable describing the displacement of the surface of a semi-infinite system from the equilibrium position are obtained in the framework of a macroscopically self-consistent approach to the surfac e response function. The calculated kinetic coefficients agree with th e results obtained in the classical limit from the quantum response fu nction in the random-phase approximation. In the limit of an incompres sible Fermi liquid the mass coefficient agrees (within a factor of ord er unity) with the expression for the mass coefficient in irrotational hydrodynamics. The velocity field corresponding to surface excitation s of a Fermi liquid is rotational. The expression for the coefficient of friction agrees with the result obtained in Svyatetsky's phenomenol ogical one-body dissipation theory. However, the coefficient of fricti on is calculated here with the same assumptions used in the treatment of collisionless Landau damping for zero sound in an infinite Fermi li quid.