On the density oscillations in finite systems

We propose an analytic form of the dispersion law for an elementary excitation in infinite nuclear matter that entails the existence of zero energy (and therefore, static) roton-like waves. An expression for the charge density of very large nuclei follows from this hypothesis. The application to the case of ²⁰⁸Pb permits a reasonable account of the available experimental data. The analysis is in agreement with the accepted view that nuclear matter is much less dense than a hard sphere Bose-gas like He II, but dense enough to display significant dispersion in the energy versus momentum curve for an elementary excitation.