Fractional Hopfions in the Faddeev-Skyrme model with a symmetry breaking potential

Abstract

We construct new solutions of the Faddeev-Skyrme model with a symmetry breaking potential admitting S1 vacuum. It includes, as a limiting case, the usual SO(3) symmetry breaking mass term, another limit corresponds to the potential m2ϕ1 2, which gives a mass to the corresponding component of the scalar field. However we find that the spacial distribution of the energy density of these solutions has more complicated structure, than in the case of the usual Hopfions, typically it represents two separate linked tubes with different thicknesses and positions. In order to classify these configurations we define a counterpart of the usual position curve, which represents a collection of loops C1, C− 1 corresponding to the preimages of the points ϕ→ = (± 1 , 0 , 0) , respectively. Then the Hopf invariant can be defined as Q= link (C1C− 1). In this model, in the sectors of degrees Q = 5,6,7 we found solutions of new type, for which one or both of these tubes represent trefoil knots. Further, some of these solutions possess different types of curves C1 and C− 1.