Black Hole Superradiance in Rotating Fluids (SURF)

预计将在黑洞附近发生的一些最基本、或许也是奇怪的过程是观测不到的。为了解决这个问题，我们利用模拟系统来研究背景流的波动，在实验中，背景流再现了有效的黑洞。在文献中，这条研究路线被称为重力的模拟模型，或简称为模拟重力。类比模型不仅提供了一个理论框架，还提供了一个实验框架，用来验证经典场和量子场的预测，这些场暴露在“极端”的时空几何中，比如快速旋转的黑洞。这个项目汇集了两位世界公认的模拟重力领域的专家，目的是将该领域推向一个新的方向：我们提议进行开创性的研究，以模拟在水和光学系统中旋转的黑洞和旋转的流体附近发生的一些奇怪的过程。特别是，我们将从理论和实验两方面研究输入波与旋转黑洞时空几何之间的相互作用，在这里，旋转流体重新创建了黑洞时空几何。这使我们能够模拟与旋转的黑色HOE相关的散射过程，称为超辐射散射。从历史的角度来看，这种辐射是霍金辐射的前身。更准确地说，黑洞超辐射是来自旋转黑洞的波的散射：如果入射波也具有少量的角动量，它将被增加的幅度反射，即它被放大，而黑洞因此失去了一些旋转能量。也有人指出，同样的物理可能发生在非常不同的系统中，例如，入射到旋转的金属(或吸收的)圆柱体上的光也可能在反射时被放大。然而，还没有人试图从实验上研究超越广义相对论的、与各种流体动力学和旋转系统相关的基本物理。我们的目标是在两个不同的流体动力学系统中提供这一有趣的基本放大机制的第一个实验证据。第一个是喷水口，它被控制，以便获得正确的边界条件，并对观测BH-SS进行优化。第二种是一种由光制成的非常规流体。在特殊介质中传播的光可以表现为流体，甚至是超流体。通过建立高度发达的光子技术，例如用于控制和测量激光波前，我们将实施非常精确的量身定做和特性化的实验。该项目的一个独特方面是两个截然不同的实验室系统之间的结合，一个使用水，另一个使用光，以解决与天体物理、流体动力学和光学系统相关的物理学中的一个突出问题。

Some of the most fundamental and perhaps bizarre processes expected to occur in the vicinity of black holes are out of observational reach. To address this issue we utilise analogue systems where we study fluctuations on a background flow that in the experiment reproduces an effective black hole. In the literature this line of research is referred to as analogue models for gravity, or simply analogue gravity. Analogue models provide not only a theoretical but also an experimental framework in which to verify predictions of classical and quantum fields exposed to 'extreme' spacetime geometries, such as rapidly rotating black holes. This project brings together two world-wide recognised experts in the field of analogue gravity with the aim of pushing the field in a new direction: we propose ground-breaking studies to mimic some of the bizarre processes occurring in the vicinity of rotating black holes from general relativity and rotating fluids in both water and optical systems. In particular, we will investigate both theoretically and experimentally the interaction between an input wave and a rotating black hole spacetime geometry, here recreated by the rotating fluid. This allows us to mimic a scattering process associated to rotating black hoes called superradiant scattering. From a historical viewpoint this kind of radiation is the precursor to Hawking radiation. More precisely, black hole superradiance is the scattering of waves from a rotating black hole: if the incoming wave also possesses a small amount of angular momentum, it will be reflected with an increased amplitude, i.e. it is amplified at the expense of the black hole that thus loses some of its rotational energy. It has also been pointed out that the same physics may take place in very different systems, for example light incident on a rotating metallic (or absorbing) cylinder may also be amplified upon reflection. Yet, no-one has ever attempted to experimentally investigate the underlying physics that extend beyond general relativity and are relevant to a variety of hydrodynamical and rotating systems.We aim to provide the first ever experimental evidence of this intriguing and fundamental amplification mechanism in two different hydrodynamical systems. The first is a water spout, controlled so that the correct boundary conditions are obtained and optimised for observing BH-SS. The second is a less conventional fluid that is made out of light. Light propagating in a special medium can behave as a fluid or even a superfluid. By building upon highly developed photonic technologies e.g. for the control and measurements of laser beam wavefronts, we will implement very precisely tailored and characterised experiments. One of the unique aspects of this project is the marriage between two very different lab-based systems, one using water the other using light, to tackle an outstanding problem in physics that is of relevance to astrophysics, hydrodynamic and optical systems.