Generalized vorticity in transitional quantum turbulence

Abstract

Transition to condensate state in the degenerate gas of bosons is studied using the Gross-Pitaevskii equation. It is shown that adiabatic invariance of an enstrophy (mean squared vorticity) based on a generalized vorticity $curl (|\psi|^2 {\bf v})/|\psi|^2$, controls dynamics of the transitional turbulence just before formation of the condensate with its tangles of quantized vortices ($|\psi|^2 {\bf v}$ is the weighted velocity field defined on the macroscopic wave function $\psi$). Scaling of the angle-averaged occupation number spectrum, $N_k \sim k^{-1}$, has been obtained for the free developing transitional turbulence for the weak nonlinear (and completely disordered) initial conditions. Results of the three-dimensional numerical simulations have been used to support the theoretical consideration.