Rotational superradiant scattering in a vortex flow

Torres, Theo; Patrick, Sam; Coutant, Antonin; Richartz, Mauricio; Tedford, Edmund W.; Weinfurtner, Silke

Abstract

When an incident wave scatters off of an obstacle, it is partially reflected and partially transmitted. In theory, if the obstacle is rotating, waves can be amplified in the process, extracting energy from the scatterer. Here we describe in detail the first laboratory detection of this phenomenon, known as superradiance 1, 2, 3, 4. We observed that waves propagating on the surface of water can be amplified after being scattered by a draining vortex. The maximum amplification measured was 14% ± 8%, obtained for 3.70 Hz waves, in a 6.25-cm-deep fluid, consistent with the superradiant scattering caused by rapid rotation. We expect our experimental findings to be relevant to black-hole physics, since shallow water waves scattering on a draining fluid constitute an analogue of a black hole 5, 6, 7, 8, 9, 10, as well as to hydrodynamics, due to the close relation to over-reflection instabilities 11, 12, 13.

Citation

Torres, T., Patrick, S., Coutant, A., Richartz, M., Tedford, E. . W., & Weinfurtner, S. (2017). Rotational superradiant scattering in a vortex flow. Nature Physics, 13, https://doi.org/10.1038/nphys4151

• Journal Article Type: Article
• Acceptance Date: Apr 25, 2017
• Online Publication Date: Jun 12, 2017
• Publication Date: Sep 1, 2017
• Deposit Date: Jun 29, 2017
• Publicly Available Date: Jun 29, 2017
• Journal: Nature Physics
• Print ISSN: 1745-2473
• Electronic ISSN: 1745-2481
• Publisher: Nature Publishing Group
• Peer Reviewed: Peer Reviewed
• Volume: 13
• DOI: https://doi.org/10.1038/nphys4151
• Keywords: Fluid dynamics, High-energy astrophysics
• Public URL: https://nottingham-repository.worktribe.com/output/966970
• Publisher URL: https://doi.org/10.1038/nphys4151
• Contract Date: Jun 29, 2017