Do event horizons exist? Information loss problem and quantum foundations

Information loss paradox in black hole physics has a structure similar to other quantum paradoxes: a combination of plausible but counterfactual classical elements and quantum features. I focus on its key semiclassical

element: formation of the event horizon.

Both logical analysis and detailed calculation lead us to consider the effects of radiation emitted prior to the final stage of collapse. Starting from the massive thin shell in spherically-symmetric spacetime it is possible to show that if a non-zero radiation flux is perceived by a distant observer the shell remains at a certain sub-Planckian distance from the Schwarzschild radius. This distance depends only on the shell's mass and evaporation rate. It was recently shown by Chen and Unruh that the process is more complicated than that: that a massive thin shell that is sandwiched between a flat interior and an exterior geometry given by the outgoing Vaidya metric becomes null in a finite proper time. I discuss how this transition is a general feature of non-zero flux at infinity, and how the newly-null shells persist on light-like trajectories.

Horizon avoidance for shells can be extended to horizon avoidance in general spherically-symmetric collapse and to some rotating shell examples. Without the event horizon the paradox is gone, but many important conceptual and observational problems just become more interesting.