Classical and quantum vortex leapfrogging in two-dimensional channels

The leapfrogging of coaxial vortex rings is a famous effect which has been noticed since the times of Helmholtz. Recent advances in ultra-cold atomic gases show that the effect can now be studied in quantum fluids. The strong confinement which characterises these systems motivates the study of leapfrogging of vortices within narrow channels. Using the two-dimensional point vortex model, we show that in the constrained geometry of a two-dimensional channel the dynamics is richer than in an unbounded domain: alongside the known regimes of standard leapfrogging and the absence of it, we identify new regimes of image-driven leapfrogging and periodic orbits. Moreover, by solving the Gross-Pitaevskii equation for a Bose-Einstein condensate, we show that all four regimes exist for quantum vortices too. Finally, we discuss the differences between classical and quantum vortex leapfrogging which appear when the quantum healing length becomes significant compared to the vortex separation or the channel size, and when, due to high velocity, compressibility effects in the condensate becomes significant.

Automated summary

This article discusses the leapfrogging of coaxial vortex rings in ultra-cold atomic gases and quantum fluids. Using the two-dimensional point vortex model and solving the Gross-Pitaevskii equation for a Bose-Einstein condensate, it was found that the dynamics of leapfrogging in narrow channels is richer than in unbounded domains, with new regimes identified. The differences between classical and quantum vortex leapfrogging were also discussed, especially when the quantum healing length and compressibility effects become significant.