# A self-consistency check for unitary propagation of Hawking quanta

## TL;DR

This paper proposes a self-consistency test for the unitarity of Hawking radiation propagation in curved spacetime, revealing potential issues with naive unitarity assumptions and discussing implications for the black hole information paradox.

## Contribution

It introduces an analogy to Feynman's double-slit analysis to test unitarity in quantum field theory near black holes, challenging assumptions about entanglement and information loss.

## Key findings

- Potential failure of naive unitarity in Hawking quanta propagation
- Implications for the black hole information paradox
- Discussion of soft-hair-memory effects as a possible resolution

## Abstract

The black hole information paradox presumes that quantum field theory in curved spacetime can provide unitary propagation from a near-horizon mode to an asymptotic Hawking quantum. Instead of invoking conjectural quantum gravity effects to modify such an assumption, we propose a self-consistency check. We establish an analogy to Feynman's analysis of a double-slit experiment. Feynman showed that unitary propagation of the interfering particles, namely ignoring the entanglement with the double-slit, becomes an arbitrarily reliable assumption when the screen upon which the interference pattern is projected is infinitely far away. We argue for an analogous self-consistency check for quantum field theory in curved spacetime. We apply it to the propagation of Hawking quanta and test whether ignoring the entanglement with the geometry also becomes arbitrarily reliable in the limit of a large black hole. We present curious results to suggest a negative answer, and we discuss how this loss of naive unitarity in QFT might be related to a solution of the paradox based on the soft-hair-memory effect.