School of Mathematics, Statistics and Physics

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Dancing vortices swap their partners

Work published by our researchers in PNAS establishes how quantum vortices interact and reconnect with each other.

Work by our quantum fluids experts - Professor Carlo Barenghi and Drs Luca Galantucci, Andrew Baggaley and Nick Parker - has established how quantum vortices interact and reconnect with each other, published in the Proceedings of the National Academy of Sciences of the USA.

Vortices are ubiquitous in moving fluids. Prominent visual examples are tornadoes and drain whirlpools, but more often vortices are there but hard to see, for example, in turbulence or the air around us. When two vortices approach each other, they “reconnect” by exchanging heads and tails. These sudden events are important in relaxing the flow as they allow the vortices to disentangle from each other and create bursts of sound waves. Indeed, vortex reconnections are one of the main sources of noise from jet engines. 

To study these fundamental events in detail, Professor Carlo Barenghi and Drs Luca Galantucci, Andrew Baggaley and Nick Parker turned to quantum fluids in the form of superfluid helium and trapped atomic Bose-Einstein condensates. Unlike in everyday fluids, where the vortices can have any strength and size, the vortices in quantum fluids are fixed by quantum mechanics to have fixed strength and size, making them well-defined objects. In particular, they study how the vortices approach each other and move away during the reconnection. 

Combining extensive results from our simulations and experimental data in the literature, they find that this motion obeys two fundamental scaling laws, common to both quantum fluids. Given recent advances in tracking individual vortices in quantum fluids, these predictions can be tested in the lab. Moreover, it raises the question of whether there is a universal reconnection behaviour which is common to classical fluids, quantum fluids and plasmas (where magnetic field lines play the role of vortices).

This work “Crossover from interaction to driven regimes in quantum vortex reconnections” appears in Proceedings of the National Academy of Sciences of the USA.

Graphic representation of Dancing vortices

published on: 10 June 2019