STRUCTURE OF THE GROUND-STATE AND LOW EXCITED-STATES OF QUANTUM FLUIDS

The structure of the ground state of a quantum fluid is described in terms of the pair correlation function and pair-pair correlation function, which are the response functions to first and second order scattering respectively. Results are presented for the pair-pair correlation function of liquid 4He obtained using two methods: a Monte Carlo simulation and a hypernetted chain approximation. These results are used to obtain the solution of the Euler-Lagrange equation for the optimum Jastrow function for the ground state of liquid 4He. The Monte Carlo calculation is in good agreement with the augmented HNC approximation. General properties of the pair correlation function are discussed in terms of its Fourier transform, the liquid structure function. A critical review is given of the present status of the Jastrow theory (and its generalizations) of the ground state of boson and fermion quantum fluids. The recent extension of the Jastrow theory to include three-body factors by Pandharipande is compared to the earlier theory of Campbell, along with a parallel discussion of the theories of the low excited states of the boson fluid by Feynman and Cohen and by Jackson and Feenberg. The importance of the three-body factors to the quantitative agreement between the theoretical and experimental phonon-roton spectrum of liquid 4He is discussed. © 1979.