On Monday, it was announced that physicists at the University of Chicago have successfully created a vortex knot, a type of physical phenomenon that was first theorized over a century ago by Lord Kelvin but has eluded scientists in the laboratory until now. In theory, vortex knots should be stable, but in practice, the loops elongate, circulate in opposite directions, collide, reconnect, and annihilate other parts of the loops.
Dustin Kleckner, a postdoctoral associate and William Irvine, an assistant professor of physics, published their research in the March edition of Nature Physics. Their work relates to many different subfields of physics because vortex knots are theorized to occur in many different media, including plasmas and superfluids. A deeper understanding of knotted structures may help scientists to understand the behavior of plasma flows, like those that occur inside the Sun, and the energy transport of complex flows in superfluids, like helium-4 at low temperatures.
Irvine speculates that the degree of “knottedness” of a system may be a new kind of physical quantity that is subject to a conservation law. If so, knottedness would be the tenth such quantity, joining angular momentum, charge/parity/time symmetry, color charge, electric charge, linear momentum, mass-energy, quantum probability, and weak isospin. “If confirmed, this would deepen our understanding of the dynamics and connections between many disparate physical fields. We don’t know if it's true or not, but I think we can finally test this in experiment. There’s actually around 50 years of theory on this subject with no clean experiments.”
In the future, Irvine and Kleckner hope to perform their experiments at a larger scale to investigate the relationship between the size of a vortex knot and its stability, as well as whether a law of conservation of knottedness exists.