Abstract

The effect of a CFT shockwave on the entanglement structure of an eternal black hole in Jackiw-Teitelboim gravity, that is in thermal equilibrium with a thermal bath, is considered. The shockwave carries energy and entropy into the black hole and heats the black hole up leading to evaporation and the eventual recovery of equilibrium. We find an analytical description of the entire relaxational process within the semiclassical high temperature regime. If the shockwave is inserted around the Page time then several scenarios are possible depending on the parameters. The Page time can be delayed or hastened and there can be more than one transition. The final entropy saddle has a quantum extremal surface that generically starts inside the horizon but at some later time moves outside. In general, increased shockwave energy and slow evaporation rate favour the extremal surface to be inside the horizon. The shockwave also disrupts the scrambling properties of the black hole. The same analysis is then applied to a shockwave inserted into the extremal black hole with similar conclusions.

Highlights

  • The black information loss paradox has inspired for over 40 years [1]

  • The effect of a CFT shockwave on the entanglement structure of an eternal black hole in Jackiw-Teitelboim gravity, that is in thermal equilibrium with a thermal bath, is considered

  • It seems as if a step change in understanding has been achieved: it is possible to calculate the flow of quantum information in a black hole background using only the semiclassical approximation. This new understanding grew out of holographic approaches to the gravitational entropy of the bulk theory [2,3,4,5]. This theory of the “generalized entropy” and the associated quantum extremal surfaces has been derived from a semi-classical calculation in a black hole background via the appearance of new saddles, i.e. instantons, known as replica wormholes [6, 7]

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Summary

Introduction

It seems as if a step change in understanding has been achieved: it is possible to calculate the flow of quantum information in a black hole background using only the semiclassical approximation This new understanding grew out of holographic approaches to the gravitational entropy of the bulk theory [2,3,4,5]. We use the scenario to ask how the entanglement structure responds when a shockwave is created in the CFT in the radiation baths The shockwave carries both energy and entropy. One of our main observations is that shockwave insertion into the black hole state allows us to analytically follow the complete evolution of the system whilst staying within the semiclassical regime This is possible in a high temperature limit in which the evaporation time scale is parametrically large compared to the inverse temperature. As this work was being completed, there appeared some related work: [9] describing the Page curve of an evaporating black hole in a related dilaton gravity model, [10] investigating islands in Schwarzschild black holes in 4 dimensions and [11] investigating islands in one dimension higher

Review: islands and the eternal black hole
The geometry
The dilaton
Entanglement dynamics
Resolving the entropy paradox via replica wormholes
The island
Shockwaves
Shockwave production
Shockwaves in the AdS region
The equilibrium state
Effect of shockwave
The exact solution
High temperature limit
Stress tensor
Vacuum coordinates
Dilaton
3.10 Entropy of the evaporating black hole
Entropy saddles
No Islands
Island with QES in front of shockwave
Island with QES behind the shockwave
Scrambling time
QES: inside or outside the horizon?
Shockwaves and the extremal black hole
The extremal black hole
The solution with a shockwave
QES in front of shockwave
QES behind shockwave
Conclusions
A Coordinate systems
Full Text
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