Role of evaporation in gravitational collapse

Abstract: We investigate the possibility that quantum effects responsible for black hole radiation do not allow for hori- zon crossing of gravitationally collapsing matter in a finite time as seen by distant observers. We consider this in the context of the collapse of evaporating massive thin dust shells using two families of metrics to describe the exterior geometry: the outgoing Vaidya metric and the retarded Schwarzschild metric. We describe how this hypothesis results in a modified equation of motion for the shell. In each case the collapse is accelerated due to evaporation, but the Schwarzschild radius is not crossed. Instead the shell is always at a certain sub-Planckian distance from this would-be horizon that depends only on the mass and evaporation rate, while a comoving observer encounters firewall-like energy density and flux with a natural cutoff.