Pure de Sitter space and the island moving back in time

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1 Citation (Scopus)


Observers in de Sitter space can only access the space up to their cosmological horizon. Assuming thermal equilibrium, we use the quantum Ryu-Takayanagi or island formula to compute the entanglement entropy between the states inside the cosmological horizon and states outside, as a function of time. We obtain a Page curve that is bound at a value corresponding to the Gibbons-Hawking entropy. At this transition an 'island' forms, which is in a significantly different location as compared to when considering black hole horizons and even moves back in time. These differences turn out to be essential for non-violation of the no-cloning theorem in combination with entanglement wedge reconstruction. This consideration furthermore introduces the need for a scrambling time, the entropy dependence of which turns out to coincide with what is expected for black holes. The model we employ has classically pure three-dimensional de Sitter space as a solution. We dimensionally reduce to two dimensions in order to take into account semi-classical effects. Nevertheless, we expect the aforementioned qualitative features of the island to persist in higher dimensions.

Original languageEnglish
Article number145012
JournalClassical and Quantum Gravity
Issue number14
Publication statusPublished - Jul 2021

Bibliographical note

Publisher Copyright:
© 2021 IOP Publishing Ltd.

Other keywords

  • de Sitter
  • generalizedentropy
  • island formula
  • Page curve
  • semi-classicalgravity
  • twodimensionalgravity


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