[Paper Review] Escaping the Interiors of Pure Boundary-State Black Holes

Ahmed Almheiri, Alexandros Mousatov+1 more|arXiv (Cornell University)|Mar 12, 2018

Black Holes and Theoretical Physics4 citations

TL;DR

This paper demonstrates that pure boundary-state black holes in AdS/CFT can be made escapable via double trace deformations in the boundary CFT, which inject negative energy into the bulk and violate the average null energy condition. By tuning the sign of the deformation coupling to the brane boundary conditions, signals can escape the black hole interior, establishing traversability analogous to traversable wormholes in the thermofield double state.

ABSTRACT

We consider a class of pure black hole microstates and demonstrate that they can be made escapable by turning on certain double trace deformations in the CFT. These microstates are dual to BCFT states prepared via a Euclidean path integral starting from a boundary in Euclidean time. These states are dual to black holes in the bulk with an End-of-the-World brane; a codimension one timelike boundary of the spacetime behind the horizon. We show that by tuning the sign of the coupling of the double trace operator to the boundary conditions on the brane the deformation injects negative energy into the black hole causing a time advance for signals behind the horizon. We demonstrate how the property of escapability in the considered microstates follows immediately from the traversability of deformed wormholes. We briefly comment on reconstruction of the black hole interior and state dependence.

Motivation & Objective

• To investigate whether pure black hole microstates with an end-of-the-world brane can be made escapable through boundary CFT deformations.
• To explore the role of state-dependent double trace deformations in enabling traversability of black hole interiors.
• To extend the concept of traversable wormholes to single-sided black holes via CFT constructions.
• To analyze how negative energy injection alters causal structure behind the horizon.
• To establish a connection between boundary CFT deformations and the reconstruction of bulk operators in the black hole interior.

Proposed method

• Constructing black hole microstates as Cardy boundary states in a CFT with a boundary in Euclidean time.
• Mapping these states to bulk spacetimes with an end-of-the-world brane behind the horizon.
• Introducing a Hamiltonian double trace deformation coupling local operators on the boundary to inject negative energy into the bulk.
• Using the AdS/CFT correspondence to relate the CFT deformation to a violation of the average null energy condition (ANEC) in the bulk.
• Computing the commutator of boundary operators in the deformed theory to probe signal propagation through the interior.
• Evaluating the commutator using a path integral approach in the limit of negligible backreaction, with explicit results for delta-function and finite-time deformations.

Experimental results

Research questions

• RQ1 Can pure black hole microstates with an end-of-the-world brane be made escapable through boundary CFT deformations?
• RQ2 How does the sign of the double trace coupling affect the causal structure behind the horizon?
• RQ3 To what extent does negative energy injection via deformations lead to traversability in single-sided black holes?
• RQ4 Can the HKLL construction be generalized to reconstruct bulk operators in the interior using deformed CFT data?
• RQ5 How does the duration and profile of the deformation affect the domain of escapability?

Key findings

• A double trace deformation with a sign tuned to the brane boundary conditions injects negative energy into the black hole, violating the average null energy condition (ANEC).
• The deformation enables signals to escape the black hole interior, making the interior causally connected to the boundary.
• For a delta-function deformation, the domain of escapability shrinks for later deformation times, indicating earlier information retrieval is more effective.
• When the deformation is turned on over a finite time interval, the domain of escapability increases, with the effect saturating at large times.
• The commutator between boundary operators becomes imaginary for negative coupling when the denominator in the amplitude turns negative, signaling non-vanishing signal propagation through the interior.
• The time it takes for information to reappear is bounded from below, with the lower bound determined by the deformation profile and operator dimensions.