  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.

Quantum Physics;General Relativity and Quantum Cosmology;High Energy Physics - Theory