Relativistic structure of charged quark stars in energy-momentum squared gravity

Abstract

Within the context of energy-momentum squared gravity (EMSG), where non-linear matter contributions appear in the gravitational action, we derive the modified TOV equations describing the hydrostatic equilibrium of charged compact stars. We adopt two different choices for the matter Lagrangian density ($\mathcal{L}_m= p$ versus $\mathcal{L}_m= -ρ$) and investigate the impact of each one on stellar structure. Furthermore, considering a charge profile where the electric charge density $ρ_{\rm ch}$ is proportional to the standard energy density $ρ$, we solve numerically the stellar structure equations in order to obtain the mass-radius diagrams for the MIT bag model equation of state (EoS). For $\mathcal{L}_m= p$ and given a specific value of $β$ (including the uncharged case when $β= 0$), the maximum-mass values increase (decrease) substantially as the gravity model parameter $α$ becomes more negative (positive). However, for uncharged configurations and considering $\mathcal{L}_m= -ρ$, our numerical results reveal that when we increase $α$ (from a negative value) the maximum mass first increases and after reaching a maximum value it starts to decrease. Remarkably, this makes it a less trivial behavior than that caused by the first choice when we take into account the presence of electric charge ($β\neq 0$).