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Rotating black holes in a draining bathtub: superradiant scattering of gravity waves

Richartz, Mauricio; Prain, Angus; Liberati, Stefano; Weinfurtner, Silke


Mauricio Richartz

Angus Prain

Stefano Liberati


In a draining rotating fluid flow background, surface perturbations behave as a scalar field on a rotating effective black hole spacetime. We propose a new model for the background flow which takes into account the varying depth of the water. Numerical integration of the associated Klein-Gordon equation using accessible experimental parameters shows that gravity waves in an appropriate frequency range are amplified through the mechanism of superradiance. Our numerical results suggest that the observation of this phenomenon in a common fluid mechanical system is within experimental reach. Unlike the case of wave scattering around Kerr black holes, which depends only on one dimensionless background parameter (the ratio a/M between the specific angular momentum and the mass of the black hole), our system depends on two dimensionless background parameters, namely the normalized angular velocity and surface gravity at the effective black hole horizon.


Richartz, M., Prain, A., Liberati, S., & Weinfurtner, S. (2015). Rotating black holes in a draining bathtub: superradiant scattering of gravity waves. Physical Review D, 91(12), Article 124018.

Journal Article Type Article
Acceptance Date May 13, 2015
Publication Date Jun 5, 2015
Deposit Date May 9, 2017
Publicly Available Date May 9, 2017
Journal Physical Review D
Print ISSN 2470-0010
Electronic ISSN 2470-0029
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 91
Issue 12
Article Number 124018
Public URL
Publisher URL
Additional Information © 2015 American Physical Society


Black holes PhysRevD.91.pdf (1.2 Mb)

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