Quantum Gravity in Closed Universes

Quantum gravity in closed universes is both relevant - our own universe has a positive cosmological constant - and elusive compared with progress on quantum gravity in open universes such as anti-de Sitter space. Many approaches are being developed; this Nordita workshop brings together experts from different backgrounds to discuss recent developments and foster collaboration. It focuses on three approaches: holography and quantum-information tools (complexity, baby universes, pseudo-entropy); explicit inclusion of the observer (von Neumann operator algebras, phases of the Euclidean path integral, observer-oriented thermodynamics); and concrete or lower-dimensional models (de Sitter JT gravity and double-scaled SYK, the Liouville complex string).