"Vortex dynamics and turbulence in two-dimensional BECs" Thomas Billam, Newcastle University

Dear All,

Quantum Systems Unit (Busch U) would like to invite you a seminar by Dr. Thomas Billam, Newcastle Unviersity, UK.

Vortex dynamics and turbulence in two-dimensional BECs

Dr. Thomas Billam, Lecturer
Newcastle University, UK

We explore the possible regimes of decaying two-dimensional quantum turbulence, and elucidate the nature of spectral energy transport, by introducing a dissipative point-vortex model with phenomenological vortex-sound interactions.  For weak dissipation and large system size we find a regime of hydrodynamic vortex turbulence in which energy is transported to large spatial scales, resembling the phenomenology of the inverse cascade observed in classical incompressible fluids, and connected to the theory of negative temperature "equilibrium" states originally introduced by Onsager. We also demonstrate the emergence of an effective enstrophy cascade in direct numerical simulations of the point-vortex model of 2D superfluid turbulence.  The cascade emerges as the vortex number is increased, with the kinetic energy spectrum exhibiting the familiar -3 spectral exponent of Kraichnan-Leith-Batchelor theory. The signatures of the cascade emerge for vortex numbers around 500, and as the vortex number increases the superfluid Kraichnan-Batchelor constant is found to approach a value of around 1.6. These results determine the parameter regime where classical turbulence phenomenology is relevant to two-dimensional quantum fluids, and point the way towards future experiments in this regime.

We look forward to seeing many of you at the seminar.
 

Quantum Systems Unit