From the Black Hole Conundrum to the Structure of Quantum Gravity

TL;DR

This paper explores the emerging structure of quantum gravity through two seemingly different but ultimately equivalent descriptions, shedding light on black hole physics and its broader cosmological implications.

Contribution

It demonstrates the physical equivalence of Euclidean path integral and holographic quantum system descriptions of black holes, clarifying key issues in black hole and quantum gravity physics.

Findings

Both descriptions yield the same physical conclusions.

Addresses black hole interior, unitarity, and interior volume puzzles.

Implications extend to cosmology and multiverse theories.

Abstract

We portray the structure of quantum gravity emerging from recent progress in understanding the quantum mechanics of an evaporating black hole. Quantum gravity admits two different descriptions, based on Euclidean gravitational path integral and a unitarily evolving holographic quantum system, which appear to present vastly different pictures under the existence of a black hole. Nevertheless, these two descriptions are physically equivalent. Various issues of black hole physics---including the existence of the interior, unitarity of the evolution, the puzzle of too large interior volume, and the ensemble nature seen in certain calculations---are addressed very differently in the two descriptions, still leading to the same physical conclusions. The perspective of quantum gravity developed here is expected to have broader implications beyond black hole physics, especially for the cosmology of the eternally inflating multiverse.