Spinning boson stars in nonlinear sigma models and Universal Relations

TL;DR

This paper explores spinning boson stars within nonlinear sigma models, revealing how target space curvature influences their structure and confirming the universality of multipole relations across models.

Contribution

It introduces spinning boson star solutions in nonlinear sigma models with curved target spaces and extends universal multipole relations to these models.

Findings

Target space curvature significantly affects boson star properties.

Universal multipole relations hold even with curved target spaces.

Abstract

Boson stars are hypothetical compact objects derived from solutions of a self-gravitating complex scalar field. In this study, we extend the traditional models by generalizing the kinetic term of the scalar field to that of a nonlinear sigma model. Concretely, we obtain spinning boson star solutions for a family of models parametrized by the curvature of their two-dimensional target manifold, as well as for various self-interaction potentials. We derive the global properties and multipolar structure of these solutions as a function of both the curvature of the target space and the strength of self-interactions. Our results suggest that a nonzero curvature in the target manifold can have a significant impact on the structure of the solutions, allowing for a range of notably different masses and degrees of compactness. However, we find that the relations between different multipoles are consistent with those for the standard complex scalar stars, and hence the universality of such relations is extended to curved target spaces.