Liquid helium in confinement.

We discuss the effects of confinement and disorder on the elementary excita tions of superfluid He-4 in porous media as observed by inelastic neutron s cattering. The three-dimensional bulk-like phonon-roton excitations of liqu id He-4 in aerogel and Vycor are the same as in bulk He-4 at low temperatur es,with the same temperature dependence. In addition to these excitations, two-dimensional layer modes, which propagate in the first few liquid layers close to the substrate, are observed in both Vycor and denser aerogels nea r the roton wave vector, with a roton-like dispersion.