Derive a closed universe directly from an external non-gravitational system

Derive the existence of a closed gravitational universe directly from the external non-gravitational system in constructions where spacetime and gravity emerge from strong quantum entanglement.

Background

The paper interprets the Karch–Randall braneworld as an explicit example in which gravitational spacetime emerges from strong quantum entanglement. It then points to related techniques involving quantum states, small-hole Cardy boundaries, and Karch–Randall branes as possible tools for extending this perspective.

An unresolved direction is to establish the closed-universe geometry from the perspective of the external non-gravitational system alone, rather than beginning with the gravitational construction. The authors identify this as a concrete question for future work.