English

Sharp threshold for reconstructing points on the line

Combinatorics 2026-04-13 v1

Abstract

For a set of nn points VRV \subseteq \mathbb{R} let G(V,p)G(V, p) be the random graph on VV where each possible edge is present independently with probability pp. We call a subset UVU \subseteq V {\emph {reconstructible}} if every injection φ:VR\varphi:V\to \mathbb{R} that preserves the distances along the edges of G(V,p)G(V, p) also preserves all pairwise distances in UU. How large is the size R\mathsf{R} of a largest reconstructible subset? Gir\~ao, Illingworth, Michel, Powierski and Scott conjectured that the answer is linear whp when p=(1+ε)/np = (1+\varepsilon)/n for every ε>0\varepsilon > 0. In this paper, we show that for every ε>0\varepsilon>0 whp there exists a reconstructible subset UU of the largest component C\mathcal{C} of the 2-core satisfying U=V(C)(1o(1))|U| = |V(\mathcal{C})|(1-o(1)), proving a stronger form of the conjecture. The bound is asymptotically best possible, since for VRV \subseteq \mathbb{R} linearly independent over Q\mathbb{Q} it is straightforward to verify that Rmax(2,V(C))\mathsf{R} \leq \max(2, |V(\mathcal{C})|). Furthermore, we extend these results to every ε:=ε(n)\varepsilon:= \varepsilon(n) satisfying ε=ω(1/lnn)\varepsilon = \omega(1/\ln n).

Keywords

Cite

@article{arxiv.2604.09176,
  title  = {Sharp threshold for reconstructing points on the line},
  author = {Georgii Zakharov},
  journal= {arXiv preprint arXiv:2604.09176},
  year   = {2026}
}

Comments

47 pages, 8 figures

R2 v1 2026-07-01T12:02:42.801Z