Boson stars in Palatini f(R) gravity

We explore equilibrium solutions of spherically symmetric boson stars in the Palatini formulation of f (R) gravity. We account for the modifications introduced in the gravitational sector by using a recently established correspondence between modified gravity with scalar matter and general relativity with modified scalar matter. We focus on the quadratic theory f (R) = R + xi R-2 and compare its solutions with those found in general relativity, exploring both positive and negative values of the coupling parameter xi. As matter source, a complex, massive scalar field with and without self-interaction terms is considered. Our results show that the existence curves of boson stars in Palatini f (R) gravity are fairly similar to those found in general relativity. Major differences are observed for negative values of the coupling parameter which results in a repulsive gravitational component for high enough scalar field density distributions. Adding self-interactions makes the degeneracy between f (R) and general relativity even more pronounced, leaving very little room for observational discrimination between the two theories.

Automated summary

In the Palatini formulation of f (R) gravity, equilibrium solutions of spherically symmetric boson stars were explored. The study compared solutions of the quadratic theory f (R) = R + xi R-2 with those in general relativity, showing similar existence curves but significant differences for negative coupling parameters leading to repulsive gravitational components. Introducing self-interactions further emphasized the similarities between f (R) and general relativity, making observational discrimination between the two theories challenging.