Local size segregation in polydisperse hard sphere fluids

The structure of polydisperse hard sphere fluids, in the presence of a wall , is studied by the Rosenfeld density functional theory. Within this approa ch, the local excess free energy depends on only four combinations of the f ull set of density fields. The case of continuous polydispersity thereby be comes tractable. We predict, generically, an oscillatory size segregation c lose to the wall, and connect this, by a perturbation theory for narrow dis tributions, with the reversible work for changing the size of one particle in a monodisperse reference fluid.