  It is proposed that the event horizon of a black hole is a quantum phase
transition of the vacuum of space-time analogous to the liquid-vapor critical
point of a bose fluid. The equations of classical general relativity remain
valid arbitrarily close to the horizon yet fail there through the divergence of
a characteristic coherence length. The integrity of global time, required for
conventional quantum mechanics to be defined, is maintained. The metric inside
the event horizon is different from that predicted by classical general
relativity and may be de Sitter space. The deviations from classical behavior
lead to distinct spectroscopic and bolometric signatures that can, in
principle, be observed at large distances from the black hole.
