DENSITY FLUCTUATION SPECTRUM OF SUPERFLUID HE-4 AT FINITE TEMPERATURES

Very recently, Woods and Svensson have reported neutron scattering experiments which indicate that the temperature-dependent weight of the elementary excitation resonance in superfluid He4 is directly proportional to the superfluid density ρs(T). We argue that this result can be easily understood within the general framework of the standard field-theoretic formulation of a Bose-condensed system and that it gives strong evidence in favor of the regularity hypothesis introduced by Hohenberg and Martin. © 1979 The American Physical Society.