# Strange stars in $f(R)$ theories of gravity in the Palatini formalism

## TL;DR

This paper investigates how different $f(R)$ gravity models in the Palatini formalism affect the structure of strange stars, revealing that for cosmologically relevant parameters the effects are negligible, but observable effects would conflict with cosmological constraints.

## Contribution

The study provides a numerical analysis of strange stars within specific $f(R)$ gravity models, comparing results to General Relativity and assessing observational viability.

## Key findings

- Modified gravity effects are negligible at cosmologically relevant scales.
- Observable effects of these models would be inconsistent with cosmological data.
- Interior solutions vary significantly depending on the $f(R)$ model and parameters.

## Abstract

In the present work we study strange stars in $f(R)$ theories of gravity in the Palatini formalism. We consider two concrete well-known cases, namely the $R+R^2/(6 M^2)$ model as well as the $R-\mu^4/R$ model for two different values of the mass parameter $M$ or $\mu$. We integrate the modified Tolman-Oppenheimer-Volkoff equations numerically, and we show the mass-radius diagram for each model separately. The standard case corresponding to the General Relativity is also shown in the same figure for comparison. Our numerical results show that the interior solution can be vastly different depending on the model and/or the value of the parameter of each model. In addition, our findings imply that i) for the cosmologically interesting values of the mass scales $M,\mu$ the effect of modified gravity on strange stars is negligible, while ii) for the values predicting an observable effect, the modified gravity models discussed here would be ruled out by their cosmological effects.