Ten shades of black

TL;DR

This paper explores how near-extremal Reissner-Nordström black holes exhibit radiation spectra that mimic black-body emission in higher-dimensional flat spacetimes, revealing a novel duality in black-hole thermodynamics.

Contribution

It demonstrates that quantum Hawking evaporation of certain black holes can be effectively described as black-body radiation in a higher-dimensional flat spacetime, highlighting a new aspect of black-hole behavior.

Findings

Black-hole radiation spectrum is distorted by curvature potential.

Gray-body factors modify the emitted radiation spectrum.

Black holes behave as perfect black-body emitters in a 9+1 dimensional spacetime.

Abstract

The holographic principle has taught us that, as far as their entropy content is concerned, black holes in $(3+1)$-dimensional curved spacetimes behave as ordinary thermodynamic systems in flat $(2+1)$-dimensional spacetimes. In this essay we point out that the opposite behavior can also be observed in black-hole physics. To show this we study the quantum Hawking evaporation of near-extremal Reissner-Nordstr\"om black holes. We first point out that the black-hole radiation spectrum departs from the familiar radiation spectrum of genuine $(3+1)$-dimensional perfect black-body emitters. In particular, the would be black-body thermal spectrum is distorted by the curvature potential which surrounds the black hole and effectively blocks the emission of low-energy quanta. Taking into account the energy-dependent gray-body factors which quantify the imprint of passage of the emitted radiation quanta through the black-hole curvature potential, we reveal that the $(3+1)$-dimensional black holes effectively behave as perfect black-body emitters in a flat $(9+1)$-dimensional spacetime.