Würzburg Seminar on Quantum Field Theory and Gravity

We analyze three saddle points of the path integral computing the partition function of the SYK model with a Maldacena-Qi coupling in the double scaling limit. The three saddle points are holographically dual to spacetimes with a black hole, without a black hole, and with a baby universe. We develop explicit chord rules that span and probe these three bulk geometries. By slicing chord diagrams open, we generate a Hilbert space description on a spatial slice for each saddle point. The Hartle-Hawking chord state for the third saddle point has genuine entanglement between the baby universe and the external spacetimes, providing evidence that a closed universe can support a nontrivial Hilbert space.