String-like solitons and their physical applications

A non-linear model of field theory on four-dimensional Minkowski space is described that admits stationary solutions with finite energy (solitons) that are localized in a neighbourhood of a one-dimensional compact contour. This contour can be a knot, link, and so on. The topological charge corresponding to soliton configurations is a Hopf invariant. Possible applications are discussed to plasma theory, the Bose–Einstein condensate, and Yang–Mills theory.