Monoidal Rips: Stable Multiparameter Filtrations of Directed Networks
Nello Blaser, Morten Brun, Odin Hoff Gardaa, Lars M. Salbu
TL;DR
The paper develops the monoidal Rips filtration for $L$-graphs valued in a symmetric duoidal lattice, unifying and extending directed and metric-based persistent constructions by replacing the max with a monoidal product $\otimes$. It proves stability results for the resulting persistence modules using a generalized network distance $d_\mathcal{N}^\oplus$, and extends the theory to multiparameter persistence when $L$ is a product of totally ordered lattices, including a novel stability bound for the sublevel Rips bifiltration. The authors implement the $p$-Rips filtration for $[0,\infty]$-graphs, demonstrate competitive or superior performance to Flagser in graph regression tasks, and show that combining different monoidal products can improve classification in point-cloud experiments. This framework provides a flexible, stable approach to topological analysis of directed networks and multiparameter datasets, with practical impact on network analysis and geometry-informed learning.
Abstract
We introduce the monoidal Rips filtration, a filtered simplicial set for weighted directed graphs and other lattice-valued networks. Our construction generalizes the Vietoris-Rips filtration for metric spaces by replacing the maximum operator, determining the filtration values, with a more general monoidal product. We establish interleaving guarantees for the monoidal Rips persistent homology, capturing existing stability results for real-valued networks. When the lattice is a product of totally ordered sets, we are in the setting of multiparameter persistence. Here, the interleaving distance is bounded in terms of a generalized network distance. We use this to prove a novel stability result for the sublevel Rips bifiltration. Our experimental results show that our method performs better than Flagser in a graph regression task, and that combining different monoidal products in point cloud classification can improve performance.
