Hitting-angle conjecture for chromatic number and neighbourhood complexes

Fix d2d\geq 2 and k{3,,d+1}k\in\{3,\dots,d+1\}. In the random Borsuk graph process, edges are added in order of decreasing geodesic distance as the angle parameter α\alpha increases. For a monotone graph property R\mathcal{R}, let α(n,R)\alpha(n,\mathcal{R}) be the random angle at which the process first attains R\mathcal{R}. Let P\mathcal{P} be the property of having chromatic number >k>k, and let Q\mathcal{Q} be the property of containing a subgraph whose neighbourhood complex is homotopy equivalent to Sk1S^{k-1}. Hitting-angle conjecture.

P(α(n,P)=α(n,Q))=1on(1).\mathbb{P}\bigl(\alpha(n,\mathcal{P})=\alpha(n,\mathcal{Q})\bigr)=1-o_n(1).

The conjecture proposes that the chromatic transition is asymptotically witnessed exactly when the relevant topological subgraph first appears. The paper notes that the analogous assertion for k=2k=2 holds, but the stated range remains open.

Sources & referencesView supporting material

Primary source

Álvaro Acitores Montero, Matthias Irlbeck, Tobias Müller and Matěj Stehlík, “Thresholds for colouring the random Borsuk graph”, arXiv:2603.05467 (2026).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.