A fourth-order topological invariant of magnetic or vortex lines

Abstract

A fourth-order topological invariant for non-dissipative magnetic or vortex configurations with zero helicity is constructed. It is an integral form of the two-link Sato-Levine topological invariant. Geometrically, the invariant is determined by the self-linking number of the curve of intersection of Seifert surfaces pulled on two linked flux tubes. © 1995.