Quantum entanglement in de Sitter space with a wall and the decoherence of bubble universes

Andreas Albrecht, Sugumi Kanno, Misao Sasaki

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


We study the effect of a bubble wall on the entanglement entropy of a free massive scalar field between two causally disconnected open charts in de Sitter space. We assume there is a delta-functional wall between the open charts. This can be thought of as a model of pair creation of bubble universes in de Sitter space. We first derive the Euclidean vacuum mode functions of the scalar field in the presence of the wall in the coordinates that respect the open charts. We then derive the Bogoliubov transformation between the Euclidean vacuum and the open chart vacua that makes the reduced density matrix diagonal. We find that larger walls lead to less entanglement. Our result may be regarded as evidence of decoherence of bubble universes from each other. We also note an interesting relationship between our results and discussions of the black hole firewall problem.

Original languageEnglish
Article number083520
JournalPhysical Review D
Issue number8
Publication statusPublished - Apr 30 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)


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