Quantum Hair and Black Hole Information

TL;DR

This paper discusses how quantum properties of gravitons around black holes encode information about their internal states, supporting the possibility of unitary black hole evaporation and addressing the information paradox.

Contribution

It explains how black hole quantum states influence emitted radiation, demonstrating a mechanism for information preservation during evaporation.

Findings

Quantum graviton states encode black hole information.

Radiation state depends linearly on initial black hole state.

Overall unitarity is compatible with semiclassical descriptions.

Abstract

It has been shown that the quantum state of the graviton field outside a black hole horizon carries information about the internal state of the hole. We explain how this allows unitary evaporation: the final radiation state is a complex superposition which depends linearly on the initial black hole state. Under time reversal, the radiation state evolves back to the original black hole quantum state. Formulations of the information paradox on a fixed semiclassical geometry describe only a small subset of the evaporation Hilbert space, and do not exclude overall unitarity.