project title: Turbulence in superfluids and in Bose condenstates
project leader: Sergey Nazarenko
access given (in days): 14
access used (in days): 6
local host: Grigory Volovik
home institution: Mathematic Institute, University of Warwick
country of institution: UK
starting date (yyyy-mm-dd): 2006-03-26
In recent experiments with quantized vortices in the Low Temperature Laboratory of HUT essentially new effects related to quantum turbulence have been observed. These observations require the modification of the current theory of turbulence in general. The new theory must be developed which should take into account the two fluid nature of superfluids; the effect of the mutual friction force between vortices and the normal component of the liquid; the effect of the Kelvin waves propagating along the vortex lines: the effect of propagating front of turbulent vorticity, etc. The new theory should be also extended to the cold gases experiencing the Bose-Einstein condensation. At the moment, these systems are becoming extremely useful tools for the experimental study of the quantum turbulence of vortices and also the wave turbulence which takes place at the first stage of the formation of the Bose-Einstein condensate.
The theory of superfluid turbulence has been developed which incorporated Kelvin waves propagating along the vortex lines. The mechanism of generation of the Kelvin waves is the reconnection of quantum vortex filaments, which creates sharp bends which transform into propagating Kelvin waves. These waves cascade their energy down-scale and their waveaction up-scale via weakly nonlinear interactions, and this is the main mechanism of turbulence at the scales less than the inter-vortex distance. Using the differential model for the Kelvin wave turbulence, it was demonstrated that the direct cascade scaling is dominating, i.e. the reconnection is equivalent to a low-frequency forcing. The project also produced 2 publications [7, 8]