Cardoso Vitor, Coutant Antonin, Richartz Mauricio, Weinfurtner Silke
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.
Phys Rev Lett. 2016 Dec 30;117(27):271101. doi: 10.1103/PhysRevLett.117.271101. Epub 2016 Dec 29.
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.
旋转超辐射在数十年前就已被理论预测，并且在黑洞物理学中是许多重要效应和现象学的主要成因。然而，旋转超辐射从未在实验中被观测到。在此，为了在实验室中探测超辐射，我们研究了放置在圆形水槽中心的旋转圆柱体周围静止流体中的声波和表面波行为。我们表明，通过对圆柱体材料进行适当选择，表面波和声波会被放大。我们研究了两种类型的不稳定性：一种在超辐射模式被限制在旋转圆柱体附近时出现，另一种不依赖于限制，对应于圆柱体的局部激发。我们的发现可以在现有的流体实验室中进行实验验证，因此，为天体物理以及流体动力学系统中快速旋转边界层产生的动力学不稳定性提供了实验探索和比较。
