Conjecture on the chromatic–cochromatic gap in random graphs

Let GG be sampled from the binomial random graph model Gn,1/2G_{n,1/2}, and let u u denote the chromatic number of GG and χˉ\bar\chi its cochromatic number, so that the gap is νχˉ\nu-\bar\chi. Here, f(n)=Θ(n/log3n)f(n)=\Theta(n/\log^3 n) means that there are positive constants bounding the ratio between the gap and n/log3nn/\log^3 n for all sufficiently large nn. Chromatic–cochromatic gap conjecture. With high probability,

χ(G)ζ(G)=Θ(n/log3n).\chi(G)-\zeta(G)=\Theta(n/\log^3 n).

The conjecture predicts the asymptotically sharp order of the difference between the chromatic and cochromatic numbers of a random graph. The paper proves a weaker lower bound of n1εn^{1-\varepsilon} for roughly 95%95\% of values of nn and conjectures that the stated order holds for all nn.

Sources & referencesView supporting material

Primary source

Annika Heckel, “The difference between the chromatic and the cochromatic number of a random graph”, arXiv:2409.17614 (2025).

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