Observation of noise correlated by the Hawking effect in a water tank

TL;DR

This study experimentally observes noise correlations in water waves caused by a Hawking-like effect, demonstrating mode pair correlations and scattering analogous to black hole radiation.

Contribution

It provides the first direct measurement of Hawking-like noise correlations in a water tank flow, linking fluid dynamics with black hole physics.

Findings

Detected clear correlations between mode pairs of opposite energies.

Measured scattering coefficients consistent with Hawking radiation analogy.

Confirmed the presence of Hawking-like noise in a controlled water flow experiment.

Abstract

We measured the power spectrum and two-point correlation function for the randomly fluctuating free surface on the downstream side of a stationary flow with a maximum Froude number $F_{\rm max} \approx 0.85$ reached above a localised obstacle. On such a flow the scattering of incident long wavelength modes is analogous to that responsible for black hole radiation (the Hawking effect). Our measurements of the noise show a clear correlation between pairs of modes of opposite energies. We also measure the scattering coefficients by applying the same analysis of correlations to waves produced by a wave maker.