So you'd usually hear that an asymptotic observer will never see an event horizon form, while an infalling observer would. This paper presents a view of the infalling observer that's a little closer to that of the asymptotic observer:
Instead it may happen that the true event horizon never forms in a gravitational collapse. We saw that an outside observer never sees formation of a horizon in finite time, not even in the full quantum treatment. What about an infalling observer? As in Hawking’s case, the infalling observer does not see radiation, but this is due to size limitations of his detectors. The mode occupation numbers we have calculated will also be the mode occupation numbers that the infalling observer will calculate, even if they be associated with frequency modes that he cannot personally detect. The infalling observer never crosses an event horizon, not because it takes an infinite time, but because there is no event horizon to cross. As the infalling observer gets closer to the collapsing wall, the wall shrinks due to radiation back-reaction, evaporating before an event horizon can form. The evaporation appears mysterious to the infalling observer since his detectors don’t register any emission from the collapsing wall. Yet he reconciles the absence of radiation with the evaporation as being due to a limitation of the frequency range of his detectors. Both he and the asymptotic server would then agree that the spacetime diagram for an evaporating black hole is as shown in Fig. 9. In this picture a global event horizon and singularity never form. A trapped surface (from within which light cannot escape) may exist temporarily, but after all of the mass is radiated, the trapped surface disappears and light gets released to infinity.
The spacetime picture that we are advocating is similar to that described in Refs. [13, 14] and, more recently, Refs. [15, 16, 17].
Edited by Startraveler, 21 July 2007 - 06:58 PM.