A physical protocol for observers near the boundary to obtain bulk information in quantum gravity
Abstract
We consider a set of observers who live near the boundary of global AdS, and are allowed to act only with simple low-energy unitaries and make measurements in a small interval of time. The observers are not allowed to leave the near-boundary region. We describe a physical protocol that nevertheless allows these observers to obtain detailed information about the bulk state. This protocol utilizes the leading gravitational back-reaction of a bulk excitation on the metric, and also relies on the entanglement-structure of the vacuum. For low-energy states, we show how the near-boundary observers can use this protocol to completely identify the bulk state. We explain why the protocol fails completely in theories without gravity, including non-gravitational gauge theories. This provides perturbative evidence for the claim that one of the signatures of holography -- the fact that information about the bulk is also available near the boundary -- is already visible in the low-energy theory of gravity.
Keywords
Cite
@article{arxiv.2008.01740,
title = {A physical protocol for observers near the boundary to obtain bulk information in quantum gravity},
author = {Chandramouli Chowdhury and Olga Papadoulaki and Suvrat Raju},
journal= {arXiv preprint arXiv:2008.01740},
year = {2021}
}
Comments
32 pages; (v2) refs added; minor textual clarifications