A note on the calculation of the long-wavelength limit of the bosonic excitation spectrum

TL;DR

This paper introduces a Green's function approach to analyze the long-wavelength excitation spectrum in interacting bosonic systems, successfully applied to liquid helium-4 and Yukawa Bose-liquid models.

Contribution

It proposes a novel decoupling method in equations of motion for Green's functions to accurately describe bosonic excitation spectra in the long-wavelength limit.

Findings

Good agreement with experimental data for helium-4

Effective modeling of nuclear matter using Yukawa Bose-liquid

Decoupling approach improves spectrum calculations

Abstract

An approach is proposed to analyze an interacting bosonic system using two-time temperature Green's functions on the collective variables. Two systems are studied: liquid helium-4 and the Yukawa Bose-liquid being a model of the nuclear matter. The suggested decoupling in the equations of motion for Green's functions yields a good description of the elementary excitation spectrum in the long-wavelength limit.