Nonminimally coupled topological-defect boson stars: Static solutions

TL;DR

This paper explores static solutions of boson stars coupled with global monopoles, revealing new phenomena such as shell formation at various radii and a universal scaling law near critical amplitudes through extensive numerical analysis.

Contribution

It uncovers novel shell structures and a universal scaling law in boson D-star configurations, expanding understanding of their gravitational properties.

Findings

Shells of bosonic matter can form far from the origin.

Shell formation occurs at critical central amplitudes.

A universal scaling law describes shell radii near critical points.

Abstract

We consider spherically symmetric static composite structures consisting of a boson star and a global monopole, minimally or non-minimally coupled to the general relativistic gravitational field. In the non-minimally coupled case, Marunovic and Murkovic have shown that these objects, so-called boson D-stars, can be sufficiently gravitationally compact so as to potentially mimic black holes. Here, we present the results of an extensive numerical parameter space survey which reveals additional new and unexpected phenomenology in the model. In particular, focusing on families of boson D-stars which are parameterized by the central amplitude of the boson field, we find configurations for both the minimally and non-minimally coupled cases that contain one or more shells of bosonic matter located far from the origin. In parameter space, each shell spontaneously appears as one tunes through some critical central amplitude of the boson field. In some cases the shells apparently materialize at spatial infinity: in these instances their areal radii are observed to obey a universal scaling law in the vicinity of the critical amplitude. We derive this law from the equations of motion and the asymptotic behavior of the fields.