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.
Highlights
Rotational superradiance was predicted theoretically decades ago, and is responsible for a number of important effects and phenomenology in black-hole physics
In curved spacetimes, superradiance leads to a wealth of interesting phenomenology, including floating orbits [9] and superradiant instabilities which lead to interesting constraints on ultralight fields [10,11,12], and even new hairy black hole configurations [13]
Sound and surface waves by a rotating analogue black hole [14,15,16,17,18]
Summary
Rotational superradiance was predicted theoretically decades ago, and is responsible for a number of important effects and phenomenology in black-hole physics. 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.
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