# Hydrostatic equilibrium configurations of neutron stars in a non-minimal geometry-matter coupling theory of gravity

## TL;DR

This paper investigates neutron star structures within a non-minimal gravity-matter coupling theory, deriving equilibrium equations and demonstrating the possibility of stable, very compact neutron stars exceeding traditional radius and mass limits.

## Contribution

It introduces a specific $f(R,L)$ gravity model and analyzes neutron star configurations, showing they can be more compact and massive than in standard gravity theories.

## Key findings

- Neutron stars can reach masses of ~2.6 solar masses.
- Stars with radii around 8 km are stable in this theory.
- Results align with observational data on neutron star sizes.

## Abstract

In this work we analyze hydrostatic equilibrium configurations of neutron stars in a non-minimal geometry-matter coupling (GMC) theory of gravity. We begin with the derivation of the hydrostatic equilibrium equations for the $f(R,L) $ gravity theory, where $R$ and $L$ are the Ricci scalar and Lagrangian of matter, respectively. We assume $f(R,L)=R/2+[1+\sigma R]L$, with $\sigma$ constant. To describe matter inside neutron stars we assume the polytropic equation of state $p=K \rho^{\gamma}$, with $K$ and $\gamma = 5/3 $ being constants. We show that in this theory it is possible to reach the mass of massive pulsars such as PSR J2215+5135. As a feature of the GMC theory, very compact neutron stars with radius $\sim8$km and $M\sim 2.6M_\odot$ are stable, thus surpassing the Buchdal and Schwarzschild radius limits. Moreover, the referred stellar diameter is obtained within the range of observational data.