Two-consecutive-values conjecture for the chromatic number of sparse random Borsuk graphs

Let G(n,α)G(n,\alpha) be the random Borsuk graph in dimension dd, let χ(G(n,α))\chi(G(n,\alpha)) denote its chromatic number, and let α0\alpha_0 be the constant supplied by the Erdős–Hajnal result mentioned in the paper's introduction. Two-consecutive-values conjecture. For all d1d\geq 1 and all sequences α=α(n)\alpha=\alpha(n) with α<α0\alpha<\alpha_0, there is a sequence of integers k=k(n)k=k(n) such that

P(χ(G(n,α)){k,k+1})=1on(1).\mathbb{P}\bigl(\chi(G(n,\alpha))\in\{k,k+1\}\bigr)=1-o_n(1).

This is presented as a weaker conjecture that might be approachable without first proving the hitting-angle conjecture. It predicts concentration of the chromatic number on two consecutive values in the indicated sparse regime and remains open.

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Primary source

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

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