Author(s): Martin Sasieta, Brian Swingle, and Alejandro Vilar López We construct a simple two-dimensional holographic model of a closed “baby” universe. The baby universe spacetime originates from the black hole interior in Jackiw-Teitelboim gravity. The holographic description is a low-temperature thermal pure state of two Sachdev-Ye-Kitaev (SYK) models. The constr… [Phys. Rev. Lett. 137, 041501] Published Mon Jul 20, 2026