Moment of inertia and compactness of quark stars within the context of $f(R,T,L_m)$ gravity

TL;DR

This study explores how $f(R,T,L_m)$ gravity influences the structure and properties of quark stars, revealing that the gravity modification and anisotropy significantly affect maximum mass and observable characteristics.

Contribution

It introduces a modified TOV framework within $f(R,T,L_m)$ gravity for quark stars and analyzes the effects of the model parameter and anisotropy on stellar properties.

Findings

Decreasing $eta$ increases maximum stellar mass.

Negative $ ext{alpha}$ allows critical configurations similar to GR.

Anisotropic pressure aligns models with observational data.

Abstract

Within the metric formalism of $f(R,T,L_m)$ gravity theories, we investigate the hydrostatic equilibrium structure of compact stars taking into account both isotropic and anisotropic pressure. For this purpose, we focus on the $f(R,T,L_m)= R+ \alpha TL_m$ model, where $\alpha$ is a free parameter. We derive the modified TOV equations and the relativistic moment of inertia in the slowly rotating approximation. Using an equation of state (EoS) for color-superconducting quark stars, we examine the effects of the $\alpha TL_m$ term on the different macroscopic properties of these stars. Our results reveal that the decrease of the parameter $\alpha$ leads to a noticeable increase in the maximum-mass values. For negative $\alpha$ with sufficiently small $\vert\alpha\vert$, we obtain a qualitative behavior similar to the general relativistic (GR) context, namely, it is possible to obtain a critical stellar configuration such that the mass reaches its maximum. However, for sufficiently large values of $\vert\alpha\vert$ keeping negative $\alpha$, the critical point cannot be found on the mass-radius diagram. We also find that the inclusion of anisotropic pressure can provide masses and radii quite consistent with the current observational measurements, which opens an outstanding window onto the physics of anisotropic quark stars. By comparing the $I-C$ relations of isotropic quark stars in modified gravity, we show that such a correlation remains almost unchanged as the parameter $\alpha$ varies from GR counterpart. On the other hand, given a fixed $\alpha$, the $I-C$ relation is insensitive to variations of the anisotropy parameter $\beta$ to $\mathcal{O}(4\%)$.