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

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.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.We acknowledge support from the University of Poitiers (ACI UP on Wave-Current Interactions 2013-2014), the Interdisciplinary Mission of CNRS (PEPS PTI 2014 DEMRATNOS), the University of Tours (ARC PoitiersTours 2014-2015), the French national research agency (ANR) HARALAB (N◦ANR-15-CE30-0017-04), the FEDER 35790-2012, and a FQXi grant of the Silicon Valley Community Foundation