English

Islands outside the horizon

High Energy Physics - Theory 2023-08-09 v4

Abstract

We consider an AdS2_2 black hole in equilibrium with a bath, which we take to have a dual description as (0+1)-dimensional quantum mechanical system coupled to a (1+1)-dimensional field theory serving as the bath. We compute the entropies of both the quantum mechanical degrees of freedom and of the bath separately, while allowing contributions from entanglement wedge "islands". We find situations where the island extends {\it outside} the black hole horizon. This suggests possible causality paradoxes which we show are avoided because of the quantum focusing conjecture. Finally, we formulate a version of the information paradox for a black hole in contact with a bath in the Hartle-Hawking state, and demonstrate the role of islands in resolving this paradox.

Keywords

Cite

@article{arxiv.1910.11077,
  title  = {Islands outside the horizon},
  author = {Ahmed Almheiri and Raghu Mahajan and Juan Maldacena},
  journal= {arXiv preprint arXiv:1910.11077},
  year   = {2023}
}

Comments

23 pages, 9 figures. New in v4: We include an argument for the conformal QNEC in 2D flat space and the QFC in two dimensions

R2 v1 2026-06-23T11:53:38.737Z