A Quantum Field Theory Approach to Simple Liquids: The Elementary Excitations of Helium 4

Abstract

In the framework of Quantum Field Theory we propose a novel approach to the theory of bosonic simple liquids, formulated in terms of a scalar, complex quantum field, the wave-field Ψ(x,t). The problem is treated in a mean-field approximation, diagonalizing the quadratic part of the Hamiltonian à la Bogoliubov and calculating in a perturbative scheme the one-loop correction to the self-energy function. We derive the dispersion relation and the dynamic and static structure factors of the liquid 4 He , obtaining results that are successfully compared with experimental data.