Bose-Einstein condensation in finite drops of alpha particles

TL;DR

This paper models finite alpha particle drops (Q-balls) using a field-theoretical approach, predicting shell-like structures and matching empirical binding energies by considering finite particle size effects.

Contribution

It introduces a mean-field model for alpha particle drops that predicts shell structures and explains binding energy data through finite size effects.

Findings

Shell-like nuclei form at high Skyrme potential strength.

Empirical binding energies are matched with enhanced gradient terms.

Finite alpha particle size explains the gradient term enhancement.

Abstract

Ground-state properties of finite drops of alpha particles (Q-balls) are studied within a field-theoretical approach in the mean-field approximation. The strong interaction of alphas is described by the scalar field with a sextic Skyrme-like potential. The radial profiles of scalar- and Coulomb fields are found by solving the coupled system of Klein-Gordon and Poisson equations. The formation of shell-like nuclei, with vanishing density around the center, is predicted at high enough attractive strength of Skyrme potential. The equilibrium values of energy and baryon number of Q-balls and Q-shells are calculated for different sets of interaction parameters. Empirical binding energies of alpha-conjugate nuclei are reproduced only if the gradient term in the Lagrangian is strongly enhanced. It is demonstrated that this enhancement can be explained by a finite size of alpha particles.