Baby Universes from Thermal Pure States in the Sachdev-Ye-Kitaev Model
Abstract
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 construction of the state relies on the insertion of a heavy matter operator, which supports the baby universe, together with a first-order thermal phase transition between a black hole phase and an empty anti-de Sitter phase. For the transition, we employ a version of the Maldacena-Qi phase transition of two coupled SYK systems. The bulk entanglement between the anti-de Sitter region and the baby universe remains O(N) below the transition, owing to the large number of light bulk fields. This entanglement admits a definition through coarse-graining over SYK couplings.
Fields of Study & Subjects
Cosmology and Gravitation Theories
Black Holes and Theoretical Physics
Pulsars and Gravitational Waves Research
Publication details
- Journal / source
- Physical Review Letters
- Publisher
- American Physical Society (APS)
- Volume
- 137
- Issue
- 4
- Pages
- 041501–041501
- Publication date
- 10 June 2026
- Language
- EN