Time in quantum gravity and black-hole information paradox

TL;DR

This paper proposes a resolution to the black-hole information paradox by showing that fundamental quantum gravity is unitary without a notion of time, allowing for apparent information loss when matter degrees of freedom are used as clocks.

Contribution

It introduces a framework where fundamental unitarity coexists with phenomenological information loss by reinterpreting matter degrees of freedom as clocks.

Findings

Fundamental quantum gravity lacks a fundamental notion of time.

Phenomenological information loss arises from matter degrees of freedom acting as clocks.

The coexistence of unitarity and information loss explains the paradox.

Abstract

The fact that canonical quantum gravity does not possess a fundamental notion of time implies that the theory is unitary in a trivial sense. At the fundamental level, this trivial unitarity leaves no room for a black-hole information loss. Yet, a phenomenological loss of information may appear when some matter degrees of freedom are reinterpreted as a clock-time. This explains how both fundamental unitarity and phenomenological information loss may peacefully coexist, which offers a resolution of the black-hole information paradox.