Hydrodynamic simulations of rotating black holes: theory & experiment

There is a broad class of systems where perturbations propagate on an effective (d+1) dimensional spacetime geometry. In the literature this phenomenon is referred to as an analogue model for gravity/effective spacetime. By now we know of a large number of systems that exhibit such behavior. Analogue models of gravity provide not only a theoretical but also an experimental framework in which to verify predictions of classical and quantum field theory in curved spacetimes. For example, the first model, proposed by W.G. Unruh in 1981, is based on the fact that sound waves propagating on an inviscid and irrotational fluid flow satisfy the Klein– Gordon equation in an effective curved background. If the velocity of the fluid exceeds the velocity of sound at some closed surface, a dumb hole, i.e. an analogue of a black hole, forms. The presence of effective horizons opens up new possibilities to experimentally explore the processes that allow rotating black holes to lose their mass and angular momentum in tabletop experiments.

An important application of analogue gravity systems is the observation of
superradiance, a phenomenon in which incident waves are amplified after being
reflected by a rotating black hole. Superradiance was first studied by Zel’Dovich for electromagnetic waves incident on a conductive rotating cylinder, but also pertains to black holes and analogue black holes. The observation of superradiance from an effective rotating black hole is the first analogue gravity experiment to study the loss of their angular momentum.

We are currently carrying out an experiment to study the effects occurring around effective horizons in an analogue gravity system. In particular, the scientific goals are to explore superradiant scattering and the black hole evaporation process. To address this issue experimentally, we utilize the analogy between waves on the surface of a stationary draining fluid/superfluid flows and the behavior of classical and quantum field excitations in the vicinity of rotating black holes.

This project will be based at the University of Nottingham at the School of Mathematical Sciences. The three external collaborators are Prof. Josef Niemela (ICTP, Italy), Prof. Stefano Liberati (SISSA, Italy) and Prof. Vitor Cardoso (Instituto Superior Técnico, Portugal). The external consultant for the experiment is Prof. Bill Unruh, who will be a regular visitor.

The PhD student will be involved in all aspects of the experiments theoretical as well experimental. We require an enthusiastic graduate with a 1st class degree in Mathematics/Physics/Engineering (in exceptional circumstances a 2(i) class degree can be considered), preferably of the MMath/MSc level. Candidates would need to be keen to work in an interdisciplinary environment and interested in learning about quantum field theory in curved spacetimes, fluid dynamics, analogue gravity, and experimental techniques such as flow visualisation (i.g. Particle Imaging or Laser Doppler Velocimetry) and surface measurements (i.g. profilometry methods).