Hints of quantum gravity from the horizon fluid

TL;DR

This paper proposes a minimal statistical model for black hole horizon fluids using the Damour-Navier-Stokes equation, linking horizon area quantization to fluid fluctuations and providing insights into quantum gravity hints.

Contribution

It introduces a novel horizon fluid model that reproduces Bekenstein-Hawking entropy and suggests area quantization through fluid fluctuation confinement.

Findings

Horizon fluid entropy matches Bekenstein-Hawking entropy at equilibrium.

A confinement scale for fluctuations implies quantized horizon area.

Bulk viscosity of fluctuations aligns with Damour's predictions.

Abstract

For many years researchers have tried to glean hints about quantum gravity from black hole thermodynamics. However, black hole thermodynamics suffers from the problem of Universality --- at leading order, several approaches with different microscopic degrees of freedom lead to Bekenstein-Hawking entropy. We attempt to bypass this issue by using a minimal statistical mechanical model for the horizon fluid based on Damour-Navier-Stokes (DNS) equation. For stationary asymptotically flat black hole spacetimes in General Relativity, we show explicitly that at equilibrium the entropy of the horizon fluid is the Bekenstein-Hawking entropy. Further we show that, for the bulk viscosity of the fluctuations of the horizon fluid to be identical to Damour, a confinement scale exists for these fluctuations, implying quantization of the horizon area. The implications and possible mechanisms from the fluid point of view are discussed.