Dark energy-like stars from nonminimally coupled scalar field

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 than 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 than that in ordinary boson stars. Moreover, we develop a universality technique which allows us to efficiently map small configurations that are easily solved by numerical methods, to large astrophysical objects.