The poset of cancellations induced by gradient dynamics in a filtered Lefschetz complex
For computational topology researchers, this provides a new combinatorial framework for simplifying persistent homology computations, though the results are incremental.
The paper introduces the depth poset of birth-death pairs in persistent homology, enabling sequences of cancellations that reduce a filtered complex to its essential homology while preserving other pairs and dependencies. An algorithm constructs this poset in two passes of standard matrix reduction.
Motivated by questions about simplification of topology, we take a discrete approach to the dependency of simplifying operations, using methods based on combinatorial gradient dynamics. We interpret the filter in persistent homology as a discrete Morse function. This lets us gradually simplify the dynamics in parallel with space and filter, while preserving homology. As a tool, we use shallow pairs, which are simultaneously birth-death pairs and combinatorial vectors. This allows us to extract topological features by the pairing of cells via persistence and simplify them using combinatorially defined cancellations. The main new concept is the depth poset of birth-death pairs, whose minimal elements are shallow pairs and whose linear extensions are sequences of cancellations that reduce the complex to its essential homology. Cancellations of birth-death pairs in a down set of this poset preserve the other birth-death pairs and the poset dependencies between them. An algorithm that constructs the depth poset in two passes of standard matrix reduction is given and proved correct.