The Erdős–Gimbel cochromatic gap conjecture

Let GG be sampled from the binomial random graph Gn,1/2G_{n,1/2}, and let χ(G)\chi(G) and ζ(G)\zeta(G) denote its chromatic and cochromatic numbers, respectively. Here, “with high probability” means with probability tending to 11 as nn\to\infty. Erdős–Gimbel cochromatic gap conjecture. With high probability,

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

This conjecture concerns the typical difference between the chromatic and cochromatic numbers of a random graph and predicts a gap of order n/log3nn/\log^3 n. The preceding discussion presents it as an expected consequence of first-moment heuristics; its resolution is not given in the supplied text.

Sources & referencesView supporting material

Primary source

Annika Heckel, “On a question of Erdős and Gimbel on the cochromatic number”, arXiv:2408.13839 (2025).

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