Nakedness and curvature strength of shell-focusing singularity in the spherically symmetric space-time with vanishing radial pressure

Abstract

It was recently shown that the metric functions which describe a spherically symmetric space-time with vanishing radial pressure can be explicitly integrated. We investigate the nakedness and curvature strength of the shell-focusing singularity in that space-time. If the singularity is naked, the relation between the circumferential radius and the Misner-Sharp mass is given by $R\approx 2y_{0} m^β$ with $ 1/3<β\le 1$ along the first radial null geodesic from the singularity. The $β$ is closely related to the curvature strength of the naked singularity. For example, for the outgoing or ingoing null geodesic, if the strong curvature condition (SCC) by Tipler holds, then $β$ must be equal to 1. We define the ``gravity dominance condition'' (GDC) for a geodesic. If GDC is satisfied for the null geodesic, both SCC and the limiting focusing condition (LFC) by Królak hold for $β=1$ and $y_{0}\ne 1$, not SCC but only LFC holds for $1/2\le β<1$, and neither holds for $1/3<β<1/2$, for the null geodesic. On the other hand, if GDC is satisfied for the timelike geodesic $r=0$, both SCC and LFC are satisfied for the timelike geodesic, irrespective of the value of $β$. Several examples are also discussed.