Linking number of vortices as baryon number

Abstract

We show that the topological degree of a Skyrmion field is the same as the Hopf charge of the field under the Hopf map and thus equals the linking number of the preimages of two points on the 2-sphere under the Hopf map. We further interpret two particular points on the 2-sphere as vortex zeros and the linking of these zero lines follows from the latter theorem. Finally we conjecture that the topological degree of the Skyrmion can be interpreted as the product of winding numbers of vortices corresponding to the zero lines, summing over clusters of vortices.