Topological definition of ring currents

Abstract

A definition of ring currents in a velocity vector field is proposed according to topological criteria: ring currents are axial vortices confined in, or rotating beyond, a separatrix, i.e., the boundary which marks the limits of the vortex. Its possible extension to magnetic-field induced, delocalized electron flow in atoms, small non-cyclic molecules and aromatic cyclic compounds is considered.