Nonminimally coupled scalar field in teleparallel gravity: boson stars

TL;DR

This paper investigates boson star solutions within teleparallel gravity, revealing unique torsion-related features like outwardly increasing energy density, and discusses how nonminimal coupling affects Lorentz invariance and the properties of these configurations.

Contribution

It introduces self-gravitating boson star solutions in teleparallel gravity with nonminimal scalar coupling, highlighting torsion-specific effects on their structure and energy distribution.

Findings

Boson stars exhibit anisotropic pressures and satisfy the dominant energy condition.

Configurations with strong coupling show outwardly increasing energy density.

Torsion effects lead to unique features not seen in curvature-based models.

Abstract

We study the nonminimally coupled complex scalar field within the framework of teleparallel gravity. Coupling of the field nonminimally to the torsion scalar destroys the Lorentz invariance of the theory in the sense that the resulting equations of motion depend on the choice of a tetrad. For the assumed static spherically symmetric spacetime, we find a tetrad which leads to a self-consistent set of equations, and we construct the self-gravitating configurations of the scalar field---boson stars. The resulting configurations develop anisotropic principal pressures and satisfy the dominant energy condition. An interesting property of the configurations obtained with sufficiently large field-to-torsion coupling constant is the outwardly increasing energy density, followed by an abrupt drop towards the usual asymptotic tail. This feature is not present in the boson stars with the field minimally or nonminimally coupled to the curvature scalar, and therefore appears to be a torsion--only effect.