Singularities, Firewalls, and Complementarity

Understand

Almheiri, Marolf, Polchinski, and Sully, recently claimed that once a black hole has radiated more than half its initial entropy (the Page time), the horizon is replaced by a "firewall" at which infalling observers burn up, in apparent violation of the equivalence principle and the postulates of black hole complementarity.

• In this paper I review the arguments for firewalls, and give a slightly different interpretation of them.
• According to this interpretation the horizon has standard properties, but the singularity is non-standard.
• The growing entanglement of the black hole with Hawking radiation causes the singularity to migrate toward the horizon, and eventually intersect it at the page time.