  We argue that a non-perturbative description of quantum gravity should
involve two (non-interacting) copies of a dual field theory on the boundary,
and describe the states of the spacetimes accordingly. So, for instance, a
complete description of the asymptotically Anti-de-Sitter spacetimes is given
by two copies of the conformal field theory associated to the global AdS
spacetime. We also argue that, in this context, gravitational collapse and
formation of a black hole may be described by unitary evolution of the dual
non-perturbative degrees of freedom.
