Abstract
A personal perspective on the black hole evaporation process is presented using, as guidelines, inputs from: (i) loop quantum gravity, (ii) simplified models where concrete results have been obtained, and, (iii) semi-classical quantum general relativity. On the one hand, the final picture is conservative in that there are concrete results that support each stage of the argument, and there are no large departures from general relativity or semi-classical gravity in tame regions outside macroscopic black holes. On the other hand, it argues against certain views that are commonly held in many quarters, such as persistence of a piece of singularity that constitutes a part of the final boundary of space–time; presence of an event horizon serving as an absolute barrier between the interior and the exterior, and the (often implicit) requirement that purification must be completed by the time the ‘last rays’ representing the extension of this event horizon reach I + .
Highlights
This diagram is routinely used in many discussions of the black hole evaporation process and the associated issue of potential information loss
Loop quantum gravity suggests a different space–time diagram that can lead to a unitary quantum evolution, where nothing dramatic happens in the low curvature, tame space–time regions
Does the second law of black hole mechanics hold for every trapping dynamical horizon (TDH) but the growth of the horizon area is directly related to the physical process of energy infall
Summary
Loop quantum gravity suggests a different space–time diagram that can lead to a unitary quantum evolution, where nothing dramatic happens in the low curvature, tame space–time regions (2) Non-trivial geometry in the trapped region: already in the semi-classical region, where curvature is much smaller than the Planck scale, the interior space–time geometry develops astonishing features once the back reaction due to the (negative energy) Hawking flux is included. Each of these three ideas constitutes a major conceptual shift with respect to Figure 1b Together they provide a more concrete basis for the general, LQG-based paradigm of the black hole evaporation process first proposed in [21], and discussed in a more concrete form in [14]. There is a discussion of issues related to space–time diagrams compatible with geometrical considerations, proposed over the last decade or so (see in particular, [24,25,26,27,28,29,30,31,32])
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