Homotopy Reconstruction via the Cech Complex and the Vietoris-Rips Complex

60 pages, 7 figuresInternational audienceWe derive conditions under which the reconstruction of a target space is topologically correct via the $\check{C}$ech complex or the Vietoris-Rips complex obtained from possibly noisy point cloud data. We provide two novel theoretical results. First, we describe sufficient conditions under which any non-empty intersection of finitely many Euclidean balls intersected with a positive reach set is contractible, so that the Nerve theorem applies for the restricted $\check{C}$ech complex. Second, we demonstrate the homotopy equivalence of a positive $\mu$-reach set and its offsets. Applying these results to the restricted $\check{C}$ech complex and using the interleaving relations with the $\check{C}$ech complex (or the Vietoris-Rips complex), we formulate conditions guaranteeing that the target space is homotopy equivalent to the $\check{C}$ech complex (or the Vietoris-Rips complex), in terms of the $\mu$-reach. Our results sharpen existing results