Non-extremal island in de Sitter gravity

Abstract This paper investigates the challenges and resolutions in computing the entanglement entropy for the quantum field theory coupled to de Sitter (dS) gravity along a timelike boundary. The conventional island formula, originally designed to calculate the fine-grained entropy for a non-gravita...

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Main Authors: Peng-Xiang Hao, Taishi Kawamoto, Shan-Ming Ruan, Tadashi Takayanagi
Format: Article
Language:English
Published: SpringerOpen 2025-03-01
Series:Journal of High Energy Physics
Subjects:
Online Access:https://doi.org/10.1007/JHEP03(2025)004
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author Peng-Xiang Hao
Taishi Kawamoto
Shan-Ming Ruan
Tadashi Takayanagi
author_facet Peng-Xiang Hao
Taishi Kawamoto
Shan-Ming Ruan
Tadashi Takayanagi
author_sort Peng-Xiang Hao
collection DOAJ
description Abstract This paper investigates the challenges and resolutions in computing the entanglement entropy for the quantum field theory coupled to de Sitter (dS) gravity along a timelike boundary. The conventional island formula, originally designed to calculate the fine-grained entropy for a non-gravitational system coupled to anti-de Sitter (AdS) gravity, encounters difficulties in de Sitter gravitational spacetime, failing to provide a physically plausible extremal island. To overcome these problems, we introduce a doubly holographic model by embedding a dS2 braneworld in an AdS3 bulk spacetime. This approach facilitates the computation of entanglement entropy through holographic correlation functions, effectively circumventing the constraints of the island formula. We demonstrate that the correct recipe for calculating entanglement entropy with dS gravity involves the non-extremal island, whose boundary is instead defined at the edge of the dS gravitational region. Our findings indicate that, during the island phase, the entanglement wedge of the non-gravitational bath includes the entire dS gravitational space. Using the second variation formula, we further show that the existence of a locally minimal surface anchored on the gravitational brane is intrinsically linked to the extrinsic curvature of the brane.
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spelling doaj-art-ce7ac87465a34f03a57aa507e64d15a82025-08-20T03:06:48ZengSpringerOpenJournal of High Energy Physics1029-84792025-03-012025315310.1007/JHEP03(2025)004Non-extremal island in de Sitter gravityPeng-Xiang Hao0Taishi Kawamoto1Shan-Ming Ruan2Tadashi Takayanagi3Center for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto UniversityCenter for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto UniversityCenter for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto UniversityCenter for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto UniversityAbstract This paper investigates the challenges and resolutions in computing the entanglement entropy for the quantum field theory coupled to de Sitter (dS) gravity along a timelike boundary. The conventional island formula, originally designed to calculate the fine-grained entropy for a non-gravitational system coupled to anti-de Sitter (AdS) gravity, encounters difficulties in de Sitter gravitational spacetime, failing to provide a physically plausible extremal island. To overcome these problems, we introduce a doubly holographic model by embedding a dS2 braneworld in an AdS3 bulk spacetime. This approach facilitates the computation of entanglement entropy through holographic correlation functions, effectively circumventing the constraints of the island formula. We demonstrate that the correct recipe for calculating entanglement entropy with dS gravity involves the non-extremal island, whose boundary is instead defined at the edge of the dS gravitational region. Our findings indicate that, during the island phase, the entanglement wedge of the non-gravitational bath includes the entire dS gravitational space. Using the second variation formula, we further show that the existence of a locally minimal surface anchored on the gravitational brane is intrinsically linked to the extrinsic curvature of the brane.https://doi.org/10.1007/JHEP03(2025)004de Sitter space2D GravityAdS-CFT CorrespondenceBlack Holes
spellingShingle Peng-Xiang Hao
Taishi Kawamoto
Shan-Ming Ruan
Tadashi Takayanagi
Non-extremal island in de Sitter gravity
Journal of High Energy Physics
de Sitter space
2D Gravity
AdS-CFT Correspondence
Black Holes
title Non-extremal island in de Sitter gravity
title_full Non-extremal island in de Sitter gravity
title_fullStr Non-extremal island in de Sitter gravity
title_full_unstemmed Non-extremal island in de Sitter gravity
title_short Non-extremal island in de Sitter gravity
title_sort non extremal island in de sitter gravity
topic de Sitter space
2D Gravity
AdS-CFT Correspondence
Black Holes
url https://doi.org/10.1007/JHEP03(2025)004
work_keys_str_mv AT pengxianghao nonextremalislandindesittergravity
AT taishikawamoto nonextremalislandindesittergravity
AT shanmingruan nonextremalislandindesittergravity
AT tadashitakayanagi nonextremalislandindesittergravity