Creation and dynamics of knotted vortices

Abstract

Knots and links have been conjectured to play a fundamental role in a wide range of physical fields, including plasmas and fluids, both quantum and classical. In fluids, the fundamental knottedness-carrying excitations occur in the form of linked and knotted vortex loops, which have been conjectured to exist for over a century. Although they have been the subject of considerable theoretical study, their creation in the laboratory has remained an outstanding experimental goal. Here we report the creation of isolated trefoil vortex knots and pairs of linked vortex rings in water using a new method of accelerating specially shaped hydrofoils. Using a high-speed scanning tomography apparatus, we measure their three-dimensional topological and geometrical evolution in detail. In both cases we observe that the linked vortices stretch themselves and then deform-as dictated by their geometrically determined energy-towards a series of local vortex reconnections. This work establishes the existence and dynamics of knotted vortices in real fluids.

Conical refraction: fundamentals and applications

“…However, there exist light beams possessing non-homogenous polarization, known as vector beams, such as the well known radial or azimuthal polarizations [101] or even beams with more involving polarization distributions [124][125][126]. The non-homogeneous polarization distribution of vector beams can lead to singular points where the SOP is exactly circular (C points), lines along which the SOP is linear (L lines) or disclinations where the instantaneous electric field is null [127][128][129][130]. Vector beams have been applied to laser material processing, optical imaging, atomic spectroscopy, and optical trapping (see [101] and the references therein), among many others.…”

On the variety of particle accumulation structures under the effect of g-jitters

“…While the bizarre variety of PAS still presents a challenge for the existing theories (Lappa, 2013b), their ubiquity suggests that their formation is a robust process (their occurrence has been demonstrated for both Marangoni flow and Rayleigh-Bénard convection, and most recently also in situations where the conditions for their existence are created artificially, Kleckner and Irvine, 2013). This means we now are in a situation where the study of PAS phenomena has reached a sort of maturity, in the sense that numerical and experimental techniques are in position to convey valuable and relevant information concerning most of the questions we may ask on the problem.…”

A Note on the Propagation of Quantized Vortex Rings Through a Quantum Turbulence Tangle: Energy Transport or Energy Dissipation?

“…The study of vortex rings is an old one, dating back at least to the 1850s 1 ; despite a long history they still provide a very active area of fluid dynamics research 2,3 . One system which provides the ideal playground to investigate the dynamics of vortex rings are those of quantum fluids such as superfluid helium and atomic Bose-Einstein condensates.…”