AdS–CFT correspondence
Establish the duality between quantum gravity in asymptotically (locally) Anti-de Sitter spacetime in n+1 dimensions and an n-dimensional conformal field theory by proving the equivalence of states, quantities, and dynamics (e.g., via equality of the CFT partition function and the gravitational path integral).
References
AdS-CFT: the (conjectured) duality between quantum gravity in (asymptotically, locally) Anti de Sitter (AdS) spacetime in $n+1$ dimensions, and a conformal quantum field theory (CFT) in $n$ dimensions.
Second, the program of gauge-gravity duality aims to extend the case of AdS/CFT to more physically meaningful field theories, but the correspondence itself, in its most illuminating example, is only conjectured rather than proven.
They specify boundary states and pairings for localized one-particle excitations within the proposed correspondence in eq.\,eq:hilbert-space-goal, while leaving the completion of the Hilbert spaces and the interacting correspondence open.