Post-firewall paradoxes
  The preeminent view that evaporating black holes should simply be smaller black holes has been challenged by the firewall paradox. In particular, this paradox suggests that something different occurs once a black hole has evaporated to one-half its original surface area. Here we derive variations of the firewall paradox by tracking the thermodynamic entropy within a black hole across its entire lifetime. Our approach sweeps away many unnecessary assumptions, allowing us to demonstrate a paradox exists even after its initial onset (when conventional assumptions render earlier analyses invalid). Our results suggest that not only is the formation of a firewall the most natural resolution, but provides a mechanism for it. Finally, although firewalls cannot have evolved for modest-sized black holes, within the age of the universe, we speculate on the implications if they were ever unambiguously observed. 
Samuel L. Braunstein and Stefano Pirandola
quant-ph gr-qc hep-th