Interferometry of black holes with Hawking radiation

TL;DR

This paper models wave optical imaging of black holes with Hawking radiation, revealing how interference effects influence the brightness and appearance of black hole images at different wavelengths.

Contribution

It introduces a numerical method to evaluate the spatial correlation function of Hawking radiation for Kerr-de Sitter black holes and analyzes the resulting wave optical images.

Findings

Short wavelength images show a star-like appearance with a photon sphere surface.

Interference can enhance brightness near the photon sphere.

Long wavelength images appear uniformly bright, obscuring emission regions.

Abstract

We investigate the wave optical imaging of black holes with Hawking radiation. The spatial correlation function of Hawking radiation is expressed in terms of transmission and reflection coefficients for scalar wave modes and evaluated by numerically summing over angular quantum numbers for the Unruh-Hawking state of the Kerr-de Sitter black hole. Then, wave optical images of an evaporating black hole are obtained by the Fourier transformation of the spatial correlation function. For short wavelength, the image of the black hole with the outgoing mode of the Unruh-Hawking state has the appearance of a star with its surface given by the photon sphere. It is found that interference between incoming modes from the cosmological horizon and reflected modes due to the scattering of the black hole can enhance brightness of images in the vicinity of the photon sphere. For a long wavelength, the entire field of view is bright, and the emission region of Hawking radiation cannot be identified.