Coherent vortex structures in quantum turbulence

This report addresses an important question discussed by the quantum turbulence community during the last decade: do quantized vortices form, in zero-temperature superfluids, coherent structures similar to vortex tubes in ordinary, viscous turbulence? So far the evidence provided by numerical simulations is that bundles of quantized vortices appear in finite-temperature superfluids, but from the interaction with existing coherent structures in the turbulent (viscous) normal fluid, rather than due to the intrinsic superfuid dynamics. In this report we show that, in very intense quantum turbulence (whose simulation was made possible by a tree algorithm), the vortex tangle contains small coherent vortical structures (bundles of quantized vortices) which arise from the Biot-Savart dynamics alone, and which are similar to the coherent structures observed in classical viscous turbulence.