Pontryagin-Thom collapse
= Pontryagin-Thom collapse
{c}
A compact smooth embedding has a <tubular neighborhood> identified with its <normal bundle>. Collapse the complement of its open disk neighborhood to the basepoint and identify the remaining quotient with the <Thom space> of that normal bundle. Pulling back its <Thom class> constructs a Gysin class. For a graph embedding into a product with Euclidean space, desuspending the auxiliary coordinates gives the corresponding wrong-way map.