Radially falling test particle approaching an evaporating black hole

Abstract

A simple model for an evaporating non-rotating black hole is considered, employing a global time that does not become singular at the putative horizon. The dynamics of a test particle falling radially towards the center of the black hole is then investigated. Contrary to a previous approach, we find that the particle may pass the Schwarzschild radius before the black hole has gone. Backreaction effects of Hawking radiation on the space-time metric are not considered, rather a purely kinematical point of view is taken here. The importance of choosing an appropriate time coordinate when describing physical processes in the vicinity of the Schwarzschild radius is emphasized. For a shrinking black hole, the true event horizon is found to be inside the sphere delimited by that radius.