chapter  15
12 Pages

The Excision Theorem

WithMarvin J. Greenberg, John R. Harper

This states that certain subspaces U ⊂ A may be cut out or excised from the space without affecting the relative homology modules. More precisely, the inclusion map (X – U, A – U) → (X, A) is called an excision if it induces an isomorphism H q ( X − U , A − U ) → H q ( X , A )