Gravity Laboratory

Hydrodynamic Black Hole Simulator

Our hydrodynamic rotating black hole simulator consists of a 3 m long, 1.5 m wide and 0.5m high rectangular water tank. Water is pumped continuously in from one end corner, and is drained through a hole (which can be varied in diameter) in the middle. The resulting fluid flow is a stationary draining vortex flow, or short a bathtub vortex flow. The setup includes a bespoke wave machine, allowing us to generate a wide range of perturbations of the air-water interface waves, which are referred to as surface waves, within our setup. To monitor and analyse the wave dynamics, we developed and implemented a variety of surface wave detection methods. The dynamical equations for surface waves interacting with the rotating vortex flow can be mapped onto massless scalar fields interacting with the gravitational potential caused by a rotating black hole in (2+1) spacetime dimensions. This setup was used to study in depth rotating black hole superradiance, ringdown and backreaction in a controlled laboratory environment.

Quantum black hole simulator

We are currently setting up a new (2+1) dimensional simulator to study black hole dynamics of rotating black hole analogues. This work is building up on the pioneering work on black hole superradiance and ring-down based on surface waves interacting with stationary draining vortex flows. In simple terms, we will implement a quantum version of our classical experiment in superfluid 4He. Superfluid 4He exhibits macroscopic quantum coherence which leads to a fluid with zero viscosity, high thermal conductivity and quantised vortices. Consequently, it is an ideal system for such a quantum simulator, as it allows mapping the dynamics of rotating black holes from macro- to nanoscales, with the additional feature of quantised angular momentum. To realise this, we needed a new purpose built facility. This activity is part of the UK-wide network initiative on Quantum Simulators for Fundamental Physics, one of the seven consortia funded through the UK Research and Innovation Quantum Technologies for Fundamental Physics call.

Cosmology simulator

In the standard cosmological picture the Universe underwent a brief period of near-exponential expansion, known as Inflation. This provides an explanation for structure formation through the amplification of perturbations by the rapid expansion of the fabric of space. This mechanism is theoretically well studied, but it cannot be directly observed in nature. We currently setting up a series of novel experiments exposing fluid systems to acceleration to simulate a variety of cosmological scenarios. To reach the needed accelerations we purpose-built a high precision mechanical shaker or employ a strong magnetic fields generated in the bore of a superconducting magnet facility at Nottingham. Our physical system consists of two immiscible fluids, and in our setups we are able to precisely control the propagation speed of the interface waves, to capture the essential dynamics of preheating and inflationary fluctuations.

Interface Metrology

We developed several optical detection schemes, including high-sensitivity interferometers, for studying the dynamics of free fluid interfaces at room temperature and pressure. One led to a patent application (in review) for a High speed 3D air-fluid interface sensor with EnShape GmbH (Jena, Germany). We are currently developing a multimode, ultra-sensitive interferometer for superfluid interfaces, thereby forming a hybrid superfluid optomechanical system.

Sonic screwdriver

We consider the wave-structure coupling between an orbital angular momentum beam and a rapidly rotating disk, to investigate a new configuration exhibiting the wave amplification effect known as rotational superradiance. While initially envisioned in terms of the scattering of an incident wave directed perpendicular to an object's rotation axis, we want to demonstrate in the context of acousto-mechanics that superradiant amplification can also occur with a vortex beam directed parallel to the rotation axis. To test his hypothesis we are currently setting up an experiment to probe a previously unexamined parameter regime in the acoustics of rotating porous media.

High-level Modelling

We are a theory-experiment mixed research group, supporting our gravity simulators with modelling techniques developed for black holes, cosmology, superfluid helium, ultra-cold atoms, optics, quantum information and quantum field theory.