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The k-cover of a point cloud X of ℝ^d at radius r is the set of all those points within distance r of at least k points of X. By varying r and k we obtain a two-parameter filtration known as the multicover bifiltration. This bifiltration has received attention recently due to being choice-free and robust to outliers. However, it is hard to compute: the smallest known equivalent simplicial bifiltration has O(|X|^{d+1}) simplices. In this paper we introduce a (1+ε)-approximation of the multicover bifiltration of linear size O(|X|), for fixed d and ε. The methods also apply to the subdivision Rips bifiltration on metric spaces of bounded doubling dimension yielding analogous results.
@InProceedings{alonso:LIPIcs.SoCG.2025.6,
author = {Alonso, \'{A}ngel Javier},
title = {{A Sparse Multicover Bifiltration of Linear Size}},
booktitle = {41st International Symposium on Computational Geometry (SoCG 2025)},
pages = {6:1--6:18},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-370-6},
ISSN = {1868-8969},
year = {2025},
volume = {332},
editor = {Aichholzer, Oswin and Wang, Haitao},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2025.6},
URN = {urn:nbn:de:0030-drops-231587},
doi = {10.4230/LIPIcs.SoCG.2025.6},
annote = {Keywords: Multicover, Approximation, Sparsification, Multiparameter persistence}
}