The Morse Complex for a Morse Function on a Manifold with Corners

David G. C. Handron

Published 2004-06-23, updated 2004-08-12Version 2

A Morse function f on a manifold with corners M allows the characterization of the Morse data for a critical point by the Morse index. In fact, a modified gradient flow allows a proof of the Morse theorems in a manner similar to that of classical Morse theory. It follows that M is homotopy equivalent to a CW-complex with one cell of dimension \lambda for each essential critical point of index \lambda. The goal of this article is to determine the boundary maps of this CW-complex, in the case where M is compact and orientable. First, the boundary maps are defined in terms of the modified gradient flow. Then a transversality condition is imposed which insures that the attaching map is non-degenerate in a neighborhood of each critical point. The degree of this map is then interpreted as a sum of trajectories connecting two critical points each counted with a multiplicity determined by a choice of orientations on the tangent spaces of the unstable manifold at each critical point.