title: Detecting Rotational Superradiance in Fluid Laboratories.
abstract: Rotational superradiance was predicted theoretically decades ago, and is chiefly responsible for a number of important effects and phenomenology in black-hole physics. However, rotational superradiance has never been observed experimentally. Here, with the aim of probing superradiance in the lab, we investigate the behavior of sound and surface waves in fluids resting in a circular basin at the center of which a rotating cylinder is placed. We show that with a suitable choice for the material of the cylinder, surface and sound waves are amplified. Two types of instabilities are studied: one sets in whenever superradiant modes are confined near the rotating cylinder and the other, which does not rely on confinement, corresponds to a local excitation of the cylinder. Our findings are experimentally testable in existing fluid laboratories and, hence, offer experimental exploration and comparison of dynamical instabilities arising from rapidly rotating boundary layers in astrophysical as well as in fluid dynamical systems.
authors.affiliation: CENTRA, Departamento de Física, Instituto Superior Técnico-IST, Universidade de Lisboa-UL, Avenida Rovisco Pais 1, 1049 Lisboa, Portugal.|Perimeter Institute for Theoretical Physics Waterloo, Ontario N2J 2W9, Canada.|Theoretical Physics Department, CERN, CH-1211 Genève 23, Switzerland.
authors.forename: Vitor
authors.initials: V
authors.lastname: Cardoso
authors.affiliation: School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: Antonin
authors.initials: A
authors.lastname: Coutant
authors.affiliation: Centro de Matemática, Computação e Cognição, Universidade Federal do ABC (UFABC), 09210-170 Santo André, São Paulo, Brazil.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Richartz
authors.affiliation: School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: Silke
authors.initials: S
authors.lastname: Weinfurtner