Signaling and the Black Hole Final State

TL;DR

This paper examines the Horowitz-Maldacena proposal for black hole final states, demonstrating that it permits signaling outside the event horizon, which could enable terrestrial tests of the theory.

Contribution

The study shows that the proposed boundary condition for black hole final states allows for detectable signaling outside the horizon, challenging previous assumptions about unitarity.

Findings

Signaling outside the event horizon is possible under the proposal.

Entangled-probe experiments can detect this signaling.

The proposal may be testable through terrestrial experiments.

Abstract

In an attempt to restore the unitarity of the evaporation process, Horowitz and Maldacena recently proposed a boundary-condition constraint for the final quantum state of an evaporating black hole at its singularity. Gottesman and Preskill have argued that the proposed constraint must lead to nonlinear evolution of the initial (collapsing) quantum state. Here we show that in fact this evolution allows signaling, making it detectable outside the event horizon with entangled-probe experiments of the kind we proposed recently. As a result the Horowitz-Maldacena proposal may be subject to terrestrial tests.