Neutron star analysis under f(R,G,Lm) gravity model

Abstract

The modified Tolman-Oppenheimer-Volkoff (TOV) equations for compact stars in the setting of $f(R,G,L_m)$ gravity are derived and numerically solved in this paper, specifically using the functional formulation $f(R,G,L_m)=R+\alpha G{L}_m$. Both quark and hadronic matter, which are characterized by physically accurate equations of state, are taken into consideration while analysing different values of the free parameter α. The influence of α on the properties of these specific stars is examined. The concluding remarks encapsulate the principal discoveries, highlighting their significance and alignment with observational data derived from the neutron star in $NGC6397$. To account for two different possibilities of the matter Lagrangian density, the study modifies the stellar structure equations by considering $L_m=p$ (where p denotes the pressure) and $L_m=-\rho$ (where ρ represents the density), allowing for accurate and reliable numerical simulations and further analysis. As expected, when $\alpha \to 0$, the traditional TOV equations of Einstein's gravity are recovered. The results indicate that the two distinct options, as, $L_m=p$ and $L_m=-\rho$, lead to markedly different outcomes on the mass-radius diagrams. In summary, this research advances our comprehension of the way $f(R,G,L_m)$ gravity affects neutron star interior structures. By providing insightful observations, it lays the groundwork for future studies and investigations in this field.