Topological current
= Topological current
{title2=$\partial_\mu j^\mu_{\rm top}=0$}
A local current whose conservation follows from field geometry rather than requiring the field equation. For <Skyrmions>, pulling back the closed volume form on the target three-sphere gives the current associated with <topological baryon number in the Skyrme model>. Its spatial integral is a <topological charge>, unchanged by smooth evolution with the prescribed boundary behaviour.