An Infalling Observer in AdS/CFT

TL;DR

This paper uses AdS/CFT to model an infalling observer's experience in a black hole, reconstructing bulk operators and addressing information loss, horizon structure, and unitarity without firewalls.

Contribution

It introduces a method to reconstruct black hole interiors in AdS/CFT, extending boundary observables beyond the horizon and analyzing implications for black hole microstates and complementarity.

Findings

Reconstruction of bulk operators beyond the horizon is possible.

Black hole microstates require exponentially precise measurements.

The approach supports black hole complementarity and unitarity without firewalls.

Abstract

We describe the experience of an observer falling into a black hole using the AdS/CFT correspondence. In order to do this, we reconstruct the local bulk operators measured by the observer along his trajectory outside the black hole. We then extend our construction beyond the black hole horizon. We show that this is possible because of an effective doubling of the observables in the boundary theory, when it is in a pure state that is close to the thermal state. Our construction allows us to rephrase questions about information-loss and the structure of the metric at the horizon in terms of more familiar CFT correlators. It suggests that to precisely identify black-hole microstates, the observer would need to conduct measurements to an accuracy of e^{-S_{BH}}. This appears to be inconsistent with the fuzzball proposal, and other recent proposals in which pure states in the ensemble of the black hole are represented by macroscopically distinct geometries. Furthermore, our description of the black hole interior in terms of CFT operators provides a natural realization of black hole complementarity and a method of preserving unitarity without firewalls.