Relativeness in Quantum Gravity: Limitations and Frame Dependence of Semiclassical Descriptions

TL;DR

This paper explores the frame-dependent nature of semiclassical descriptions in quantum gravity, especially in black hole physics, proposing a duality that preserves information and avoids firewalls.

Contribution

It introduces the concepts of extreme relativeness and spacetime-matter duality, providing a new framework for understanding black hole information and interior consistency.

Findings

Black hole degrees of freedom exhibit extreme relativeness.

Spacetime-matter duality explains dual roles of these degrees of freedom.

The framework avoids firewall paradoxes and supports unitarity.

Abstract

Consistency between quantum mechanical and general relativistic views of the world is a longstanding problem, which becomes particularly prominent in black hole physics. We develop a coherent picture addressing this issue by studying the quantum mechanics of an evolving black hole. After interpreting the Bekenstein-Hawking entropy as the entropy representing the degrees of freedom that are coarse-grained to obtain a semiclassical description from the microscopic theory of quantum gravity, we discuss the properties these degrees of freedom exhibit when viewed from the semiclassical standpoint. We are led to the conclusion that they show features which we call extreme relativeness and spacetime-matter duality---a nontrivial reference frame dependence of their spacetime distribution and the dual roles they play as the "constituents" of spacetime and as thermal radiation. We describe black hole formation and evaporation processes in distant and infalling reference frames, showing that these two properties allow us to avoid the arguments for firewalls and to make the existence of the black hole interior consistent with unitary evolution in the sense of complementarity. Our analysis provides a concrete answer to how information can be preserved at the quantum level throughout the evolution of a black hole, and gives a basic picture of how general coordinate transformations may work at the level of full quantum gravity beyond the approximation of semiclassical theory.