Q-stars in scalar-tensor gravitational theories

TL;DR

This paper investigates q-stars within scalar-tensor theories of gravity, specifically Brans-Dicke theory, showing how star properties vary with the scalar field coupling parameter compared to General Relativity.

Contribution

It provides the first detailed analysis of q-star properties in Brans-Dicke and general scalar-tensor theories, highlighting deviations from General Relativity based on the coupling parameter.

Findings

Star mass, radius, and particle number are slightly larger than in General Relativity.

Results approach those of General Relativity as the Brans-Dicke parameter tends to infinity.

Scalar-tensor effects cause a few percent increase in star parameters.

Abstract

We study q-stars in Brans-Dicke gravitational theory. We find that when the Brans-Dicke constant, $\omega_{\textrm{BD}}$, tends to infinity, the results of General Relativity are reproduced. For other values of $\omega_{\textrm{BD}}$, the particle number, mass and radius of the star and the absolute value of the matter field are a few percent larger than in the case of General Relativity. We also investigate the general scalar-tensor gravitational theory and find that the star parameters are a few percent larger than in the case of General Relativity.