Backreaction in an Analogue Black Hole Experiment

Analogue models of gravity, particularly fluid mechanical analogues, have been very successful in mimicking the behavior of fields around black holes. However, hydrodynamic black holes are externally driven systems whose effective mass and angular momentum are set by experimental parameters, and, as such, no appreciable internal backreaction is expected to take place. On the contrary, we show using a rotating draining vortex flow that a fluid system of finite size responds to the presence of waves on timescales much longer than the wave dynamics, which leads to a significant global change in the total mass of our system. This backreaction is encapsulated by a dynamical metric, raising the possibility of studying backreaction in analogue black hole spacetimes.