Information Recovery From Black Holes

TL;DR

The paper argues that in quantum gravity, black hole information is theoretically recoverable from infinity due to discrete energy spectra, but practical measurement limitations lead to perceived information loss.

Contribution

It demonstrates that finite black hole states can be distinguished from infinity, linking boundary measurements to quantum state identification.

Findings

Finite black hole states are distinguishable via boundary measurements.

Discrete energy spectra imply non-degenerate states except for symmetries.

Information loss is a practical issue due to measurement resolution, not fundamental.

Abstract

We argue that if black hole entropy arises from a finite number of underlying quantum states, then any particular such state can be identified from infinity. The finite density of states implies a discrete energy spectrum, and, in general, such spectra are non-degenerate except as determined by symmetries. Therefore, knowledge of the precise energy, and of other commuting conserved charges, determines the quantum state. In a gravitating theory, all conserved charges including the energy are given by boundary terms that can be measured at infinity. Thus, within any theory of quantum gravity, no information can be lost in black holes with a finite number of states. However, identifying the state of a black hole from infinity requires measurements with Planck scale precision. Hence observers with insufficient resolution will experience information loss.