  A reformulation of the calculation of the semi-classical energy-momentum
tensor on a Schwarzschild background, the Bousso covariant entropy bound, and
the ER=EPR conjecture of Maldacena and Susskind taken together suggest a
scenario for the evaporation of a large spherically symmetric black hole formed
in gravitational collapse in which 1) the classical r = 0 singularity is
replaced by an initially small non-singular core inside an inner apparent
horizon, 2) the radius of the core grows with time due to the increasing
entanglement between Hawking radiation quanta outside the black hole and the
Hawking partner quanta in the core contributing to the quantum back-reaction,
and 3) by the Page time the trapped surfaces disappear and all quantum
information stored in the interior is free to escape. The scenario preserves
unitarity without any need for a "firewall" in the vicinity of the outer
apparent horizon. Qbits in the Hawking radiation are never mutually entangled,
and their number never exceeds the Bekenstein-Hawking entropy of the black
hole. The quantum back-reaction, while it must be very large in the deep
interior of the black hole, can be described semi-classically in the vicinity
of the outer apparent horizon up until close to the Page time. An explicit toy
model for the metric in the interior of the black hole, and how its associated
energy-momentum tensor can be continued to the exterior in a semi-classical
approximation, is discussed.
