Singularity Avoidance in Gravitational Collapse of an Inhomogeneous Fluid in Rastall Gravity

Abstract: Various types of inhomogeneous collapse models in general relativity (GR) lead to the formation of spacetime singularities either visible or hidden by a spacetime horizon. Our aim in the present work is to search for nonsingular models in Rastall gravity that arise as the final outcomes of spherically symmetric gravitational collapse of an inhomogeneous matter cloud. We firstly assume linear equations of state (EoS) for radial and tangential pressure profiles, i.e., $p_r=w_r\rho$ and $p_\theta=w_\theta\rho$, then we set the Rastall parameter in such a way that the effective pressure in radial direction vanishes and examine the conditions under which the spacetime singularity can be avoided. We find exact nonsingular collapse solutions for which the collapsing cloud reaches a minimum physical radius at a finite amount of time and then rebounds to an expanding phase where the matter shells start moving away from each other. The solutions we obtain respect the weak energy condition (WEC), which is important for the physical validity of the model.