Numerical evolutions of boson stars in Palatini $f(\mathcal{R})$ gravity

TL;DR

This paper studies the evolution of boson stars within Palatini $f( ext{R})$ gravity using Numerical Relativity, revealing stable, unstable, and collapse scenarios influenced by the modified gravity parameter.

Contribution

It introduces a novel method linking Palatini $f( ext{R})$ gravity to General Relativity with modified scalar matter, enabling numerical simulations of boson stars in this gravity theory.

Findings

Boson stars can be stable or unstable in Palatini $f( ext{R})$ gravity.

Unstable stars may disperse, migrate, or collapse into baby universes.

The behavior depends on the coupling parameter $\xi$.

Abstract

We investigate the time evolution of spherically symmetric boson stars in Palatini $f(\mathcal{R})$ gravity through Numerical Relativity computations. Employing a novel approach that establishes a correspondence between modified gravity with scalar matter and General Relativity with modified scalar matter, we are able to use the techniques of Numerical Relativity to simulate these systems. Specifically, we focus on the quadratic theory $f(\mathcal{R})=\mathcal{R}+\xi\mathcal{R}^2$ and compare the obtained solutions with those in General Relativity, exploring both positive and negative values of the coupling parameter $\xi$. Our findings reveal that boson stars in Palatini $f(\mathcal{R})$ gravity exhibit both stable and unstable evolutions. The latter give rise to three distinct scenarios: migration towards a stable configuration, complete dispersion, and gravitational collapse leading to the formation of a baby universe structure.