Dark energy-like stars from nonminimally coupled scalar field

TL;DR

This paper investigates scalar field configurations with nonminimal coupling to gravity, revealing dark energy-like stars with unique properties, including negative pressures and higher compactness, extending the understanding of exotic stellar objects.

Contribution

It introduces a universality technique for mapping small scalar configurations to large astrophysical objects, highlighting differences from ordinary boson stars due to nonminimal coupling.

Findings

Configurations resemble dark energy stars with negative pressures.

Maximum compactness exceeds that of ordinary boson stars.

Mass limits are reduced due to energy condition violations.

Abstract

We show that even a rather minimal extension of the Einstein - Hilbert action by a nonminimal coupling of the scalar field to the Ricci curvature scalar results in configurations that resemble more the dark energy stars then the ordinary boson stars. Even though many of those configurations are endowed by negative principal pressures, the strong energy condition, as a signal of repulsive gravity, is not significantly violated in these configurations. When imposing restrictions on matter from energy conditions we find that the maximally allowed masses are shifted to the lower values due to the violation of the weak and dominant energy conditions. We also calculate the effective compactness and show that its maximum value is attained in the region of negative pressures, and is greater then that in ordinary boson stars. Moreover, we develop a universality technique which allows to efficiently map small configurations, that are easily solved by numerical methods, to large astrophysical objects.