Is it guaranteed to be true that a “white hole” would have to look like the reverse of a black hole in all respects, including quantum phenomena like Hawking radiation?
possible to have such a completely time-reversed black hole just by T-symmetry, but I wonder if there are clear arguments in “white hole thermodynamics” that would rule out a different kind of white hole that was increasing the entropy of the region it was sitting in rather than decreasing it. If it was possible to have an entropy-increasing white hole then you’d need additional arguments to explain why we don’t see any, but if a white hole would require photons from its surroundings to converge on its event horizon as time-reversed Hawking radiation, then I suppose the absence of white holes could then be explained on thermodynamic grounds alone.
