Dec 15 – 18, 2020
Online (Zoom)
Asia/Tokyo timezone

Entanglement between two disjoint universes

Dec 18, 2020, 2:00 PM
Online (Zoom)

Online (Zoom)

The necessary information (links, IDs and passwords) will be sent to the participants by E-mail before the workshop starts.


Dr Tomonori Ugajin (YITP)


We use the replica method to compute the entanglement entropy of a universe without gravity entangled in a thermofield-double-like state with a disjoint gravitating universe. Including wormholes between replicas of the latter gives an entropy functional which includes an "island" on the gravitating universe. We solve the back-reaction equations when the cosmological constant is negative to show that this island coincides with a causal shadow region that is created by the entanglement in the gravitating geometry. At high entanglement temperatures, the island contribution to the entropy functional leads to a bound on entanglement entropy, analogous to the Page behavior of evaporating black holes. We also apply the formalism to black holes in de Sitter space, and find similar islands.

Presentation materials