VLASOV DYNAMICS OF A SEMI-INFINITE SYSTEM

The solutions of the linearized Vlasov equation for a semi-infinite system are obtained and discussed. These solutions are based on the van Kampen method for homogeneous systems. The relevant aspects of the surface behavior are discussed in terms of the boundary conditions for the fixed surface, as well as for the free surface. An ad hoc surface tension is added to the model to simulate gradient effects and the finite range of nuclear forces. The comparison of the amplitudes of the fluctuations of the nucleon density and of the displacement of the surface along the perpendicular direction provides a suitable criterion to establish a distinction between predominantly volume-type modes and predominantly surface-type modes.