Michikazu Kobayashi (Kochi University of Technology): Topologically stable hydrodynamic vortex knot in Bose-Einstein condensates

Lord Kelvin proposed that atoms are formed as hydrodynamic vortex knots in aether fluid. However, they typically untie through reconnections, unlike stable vortex unknotting rings. The same holds in superfluids where vortices have quantized circulation, making them topologically stable. For over 150 years, hydrodynamically stable vortex knots have been sought both experimentally and theoretically. Here, we present the demonstration of hydrodynamically stable vortex knots and links in Bose-Einstein condensates of ultracold atomic gases and confirm it through dynamic simulations. Our method creates stable knotted vortex structures in systems where reconnections are prohibited. We further propose the necessary condition for creating topologically stable vortex knots and rings. MK, Y. Nozaki, Y. Koda, and M. Nitta, arXiv:2410.07470