Seminar detail: Closed Universes from Symmetric Orbifolds

Date&Time	Tue Apr 21 2026 (17:00 - 18:00)
Speaker	Tomonori Ugajin
Affiliation	Rikkyo University
Title	Closed Universes from Symmetric Orbifolds
Abstract	A proper formulation of quantum gravity in closed universes remains an important open problem. Recently, in the context of the AdS/CFT correspondence, a connection has been suggested between bulk closed universes and states for which the large- N limit is not well-defined. 　In this work, we construct such states in two-dimensional symmetric orbifold CFTs and show that a type II_{1} von Neumann algebra naturally acts on them. Furthermore, we compute correlation functions in a class of partially thermal entangled (PET) states by extending Bantay’s formula, and demonstrate that they exhibit the factorization properties expected from the existence of closed universes in the bulk.
Remarks
Slide/Video