Related Experiment Video
Updated: Apr 30, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Onsager-Kraichnan condensation in decaying two-dimensional quantum turbulence
T P Billam1, M T Reeves1, B P Anderson2
1Jack Dodd Centre for Quantum Technology, Department of Physics, University of Otago, Dunedin 9016, New Zealand.
Researchers developed a new model for 2D quantum turbulence in superfluids, mapping quantum vortices to a point-vortex model. This allows sampling of vortex states, revealing negative-temperature states with energy condensation, termed Onsager-Kraichnan condensates (OKCs).
Area of Science:
- Fluid Dynamics
- Quantum Mechanics
- Statistical Physics
Background:
- Onsager's point-vortex model is key for 2D classical turbulence.
- A first-principles model for superfluid turbulence is lacking.
- Quantum vortices in superfluids are complex to analyze statistically.
Purpose of the Study:
- Develop a first-principles point-vortex model for 2D superfluids.
- Enable Monte Carlo sampling of the vortex microcanonical ensemble.
- Investigate the full range of vortex states in 2D superfluids.
Main Methods:
- Mapping quantum vortices from the 2D Gross-Pitaevskii equation (GPE) to a point-vortex model.
- Utilizing Monte Carlo methods for ensemble sampling.
- Performing damped GPE simulations.
Main Results:
- Successfully mapped GPE quantum vortices to a point-vortex model.
- Characterized vortex states from positive to negative temperatures.
- Identified negative-temperature states with vortex clustering and kinetic energy condensation (Onsager-Kraichnan condensates - OKC).
Conclusions:
- The developed model enables statistical analysis of 2D superfluid turbulence.
- Onsager-Kraichnan condensates emerge dynamically in decaying 2D quantum turbulence.
- These states are potentially observable in atomic Bose-Einstein condensate experiments.
Related Concept Videos
Phase Transitions: Vaporization and Condensation
The de Broglie Wavelength
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
Atomic Nuclei: Nuclear Relaxation Processes
The Quantum-Mechanical Model of an Atom
Phase Transitions: Sublimation and Deposition

