Hawking area law in quantum gravity

TL;DR

This paper explores the implications of the LIGO--Virgo--KAGRA verification of Hawking's area law for quantum gravity theories, showing it constrains models to specific conditions and confirming the entropy-area law.

Contribution

It demonstrates that observed black hole mergers impose strict conditions on quantum gravity models and confirms the classical entropy-area law as a consequence of Hawking's law.

Findings

Black hole mergers can be explained by local Stelle gravity and nonlocal quantum gravity theories under specific conditions.

The classical black-hole entropy-area law holds as a consequence of Hawking's area law.

The work constrains quantum gravity theories by showing the absence of certain terms and poles in the graviton propagator.

Abstract

We show that the LIGO--Virgo--KAGRA (LVK) verification of Hawking area law carries profound consequences for quantum gravity if such a law is postulated to hold exactly. The observed mergers can be produced in local Stelle gravity and in nonlocal quantum-gravity theories with entire or fractional form factors either by (i) singular Ricci-flat black holes or (ii) possibly regular classical black holes under very restrictive conditions: absence of $R^2$ and (Riemann)${}^2$ terms in the action, absence of extra real poles in the graviton propagator, and positivity of its spectral representation. To date, this is the strongest simplification of the ambiguities of this class of theories. We also prove that the classical standard black-hole entropy-area law holds as a consequence of Hawking area law, and provide a rigorous realization of Barrow's fractal black holes otherwise.