  Canonical quantization of local field theories is classical black hole
spacetimes with a single horizon leads to a particle number density with a
thermal distribution in equilibrium at the Hawking temperature. A complete
treatment including non-local quantum gravity effects has shown however that
the full "thermal vacuum" of the theory is the false vacuum. In this work we
find the true vacuum consistent with the complete semiclassical analysis of
quantum black holes. The theory is described by a "microcanonical" quantum
field theory with fixed energy E = M, the mass of the black hole.
Considerations making use of the microcanonical density matrix as well as the
idempotency condition show that particles in black hole backgrounds are
described by pure states, unlike the canonical formulation.
