Hopf invariant
= Hopf invariant
{wiki=Hopf_invariant}
The Hopf invariant is a topological invariant that arises in the study of mappings between spheres, particularly in the context of homotopy theory and homotopy groups of spheres. Named after Heinz Hopf, the invariant provides a way to classify certain types of mappings and can be used to distinguish between different homotopy classes of maps.