Correlations in Bose Fluids I. An Elementary Excitation and Its Effective Hamiltonian : Sunakawa's Collective Description

概要

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An elementary excitation which is evolved from the unperturbed Bogoljubov excitation adiabatically is constructed for Sunakawa's Hamiltonian of the collective description. By introducing the Feynman excitation into the theory we get a method to calculate the excitation energy perturbationally. It is shown that Sunakawa's excitation energy is nothing but the present one in the lowest order. The excitation energy at finite temperatures is shown to be almost independent of temperature, failing to explain the experimental temperature variation of the phonon-roton spectrum in liquid helium II. The effective interaction among the present excitations is made up in the lowest approximation in order to attack the possibility of forming a new type of correlation below the transition temperature, which is able to explain the experiment. Very rough discussion is presented on the above possibility, leaving the detailed study to a subsequent article.
理論物理学刊行会の論文
1974-09-25