Constrained semi-infinite nuclear matter and droplet model theorems on nuclei surface structure

Using a completely general constrained energy-density method, we prove two theorems, describing the surface structure of asymmetric semi-infinite nuclear matter, earlier demonstrated only in the droplet model (DM) context by Myers and Swiatecki. As a consequence a well-known relation between neutron skin-thickness and the surface stiffness coefficientQ is shown to have a much wider validity than in the DM context. Moreover we exhibit a microscopic reason for a relation, (earlier quoted as unexpected), between DM surface coefficients and the volume-symmetry coefficientJ.