Bose condensation and the static pair correlation function in 4He

An investigation is made of the implications that the presence of a Bose condensate (BC) has for static pair correlation function, g(r). The scattering of incident radiation from many particle states which contribute to the BC, is compared with that from states which do not. It is shown that in the former, the scattering density of each atom is delocalised in position space, wheras in the latter it is localised, i.e. quite different physical scattering processes occur from the two types of state. A simple model of a dilute gas, based on variational wavefunctions of the ground state, predicts that g(r) in the ground state depends directly on the condensate fraction f. The paper provides support for the intuitive idea that localization of atoms in momentum space is directly associated with a delocalisation in position space and consequent loss of spatial correlations