# Generalized Unruh effect: A potential resolution to the black hole information paradox

## TL;DR

This paper extends the Unruh effect to excited states, proposing a mechanism by which information inside black holes could be partially recovered from Hawking radiation, potentially resolving the black hole information paradox.

## Contribution

It generalizes the vacuum-Unruh effect to excited states and suggests a new way to retrieve black hole interior information from Hawking radiation.

## Key findings

- Unruh mode induces coherent excitation at the horizon.
- Mapping from density matrix to pseudo-thermal state is one-to-one.
- Black hole information may be preserved better than previously thought.

## Abstract

We generalize the vacuum-Unruh effect to arbitrary excited states in the Fock space and find that the Unruh mode at the horizon induces coherent excitation on the canonical background ensemble measured by an accelerated observer. When there is only one type of Unruh mode in the system, for example, the ones outgoing from a black hole horizon, the mapping from an arbitrary density matrix on the maximal foliation to a vector space spanned by the pseudo-thermal density matrix on the partitioned spacetime wedge is one-to-one. Hence we propose that the information of the particles that are inside a collapsing shell, thus inside the asymptotic black hole horizon is at least partially retrievable by measuring the deviation of the Hawking radiation from the black body radiation spectrum. This work shows that the long-standing black hole information confusion might come from overlooking the possibility that the information could be preserved much better than we have expected in a seemingly non-unitary process when the partitions of the system are strongly entangled.

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Source: https://tomesphere.com/paper/2302.12256