Morse-Maxwell Theory for Directed Acyclic Graph

Source abstract

The Maxwell graph of a directed acyclic graph is obtained from its iterated basin and hill boundaries. The unweighted counts of extrema at these levels need not satisfy Morse inequalities. We assign multiplicities by the reduced homology of lower and upper order links and retain the vertices with nonzero local homology. The resulting graph preserves both boundary hierarchies, the local groups, and the homology of all sublevel and superlevel order complexes. Its descending and ascending Morse numbers satisfy the weak and strong Morse inequalities over any field. We also construct a Morse chain complex and compute the local groups in several examples. Finally, we consider homology on the original Maxwell graph and prove analogous inequalities for path homology using relative local groups.