All black holes in Lemaître-Tolman-Bondi inhomogeneous dust collapse

Within the Lemaître-Tolman-Bondi formalism for the gravitational collapse of inhomogeneous dust, we analyze the parameter space that leads to the formation of a globally covered singularity (i.e. a black hole) when some physically reasonable requirements are imposed (namely, a positive, radially decreasing and quadratic profile for the energy density and the avoidance of shell crossing singularities). It turns out that a black hole can occur as the endstate of collapse only if the singularity is simultaneous, as in the standard Oppenheimer-Snyder scenario. Given a fixed density profile, there is one velocity profile for the infalling particles that will produce a black hole. All other allowed velocity profiles will terminate the collapse in a locally naked singularity.