Structure of boson systems beyond the mean-field

TL;DR

This paper explores the detailed structure and correlations in boson systems beyond mean-field approximations, using advanced analytical and numerical methods to understand stability, decay, and exotic states.

Contribution

It introduces a hyperspherical adiabatic approach with two-body wave function decomposition to analyze boson condensates beyond mean-field theory.

Findings

Efimov-like states are very narrow

Stability conditions for boson systems are established

Comparison with mean-field results shows qualitative agreement

Abstract

We investigate systems of identical bosons with the focus on two-body correlations. We use the hyperspherical adiabatic method and a decomposition of the wave function in two-body amplitudes. An analytic parametrization is used for the adiabatic effective radial potential. We discuss the structure of a condensate for arbitrary scattering length. Stability and time scales for various decay processes are estimated. The previously predicted Efimov-like states are found to be very narrow. We discuss the validity conditions and formal connections between the zero- and finite-range mean-field approximations, Faddeev-Yakubovskii formulation, Jastrow ansatz, and the present method. We compare numerical results from present work with mean-field calculations and discuss qualitatively the connection with measurements.