Sigma Model Q-balls and Q-Stars

TL;DR

This paper introduces a new class of Q-balls and Q-stars within a non-linear sigma model, analyzing their properties, differences from traditional Q-balls, and their gravitationally bound counterparts, revealing unique bounds and solution types.

Contribution

The paper presents the discovery and analysis of sigma model Q-balls and Q-stars, highlighting their distinct properties and differences from conventional Q-balls, including bounds on scalar fields and non-solitonic solutions.

Findings

Existence of sigma model Q-balls and Q-stars with unique properties.

Identification of an upper bound on the central scalar field.

Discovery of non-solitonic solutions related to sigma star solutions.

Abstract

A new kind of Q-balls is found: Q-balls in a non-linear sigma model. Their main properties are presented together with those of their self-gravitating generalization, sigma model Q-stars. A simple special limit of solutions which are bound by gravity alone (``sigma stars'') is also discussed briefly. The analysis is based on calculating the mass, global U(1) charge and binding energy for families of solutions parameterized by the central value of the scalar field. Two kinds (differing by the potential term) of the new sigma model Q-balls and Q-stars are analyzed. They are found to share some characteristics while differing in other respects like their properties for weak central scalar fields which depend strongly on the form of the potential term. They are also compared with their ``ordinary'' counterparts and although similar in some respects, significant differences are found like the existence of an upper bound on the central scalar field. The sigma model Q-stars also contain non-solitonic solutions whose relation with sigma star solutions is discussed.