{ "id": "1508.03870", "version": "v1", "published": "2015-08-16T21:52:36.000Z", "updated": "2015-08-16T21:52:36.000Z", "title": "Chromatic thresholds in dense random graphs", "authors": [ "Peter Allen", "Julia Böttcher", "Simon Griffiths", "Yoshiharu Kohayakawa", "Robert Morris" ], "comment": "36 pages (including appendix), 1 figure; the appendix is copied with minor modifications from arXiv:1108.1746 for a self-contained proof of a technical lemma", "categories": [ "math.CO" ], "abstract": "The chromatic threshold $\\delta_\\chi(H,p)$ of a graph $H$ with respect to the random graph $G(n,p)$ is the infimum over $d > 0$ such that the following holds with high probability: the family of $H$-free graphs $G \\subset G(n,p)$ with minimum degree $\\delta(G) \\ge dpn$ has bounded chromatic number. The study of the parameter $\\delta_\\chi(H) := \\delta_\\chi(H,1)$ was initiated in 1973 by Erd\\H{o}s and Simonovits, and was recently determined for all graphs $H$. In this paper we show that $\\delta_\\chi(H,p) = \\delta_\\chi(H)$ for all fixed $p \\in (0,1)$, but that typically $\\delta_\\chi(H,p) \\ne \\delta_\\chi(H)$ if $p = o(1)$. We also make significant progress towards determining $\\delta_\\chi(H,p)$ for all graphs $H$ in the range $p = n^{-o(1)}$. In sparser random graphs the problem is somewhat more complicated, and is studied in a separate paper.", "revisions": [ { "version": "v1", "updated": "2015-08-16T21:52:36.000Z" } ], "analyses": { "keywords": [ "dense random graphs", "chromatic threshold", "sparser random graphs", "significant progress", "high probability" ], "note": { "typesetting": "TeX", "pages": 36, "language": "en", "license": "arXiv", "status": "editable", "adsabs": "2015arXiv150803870A" } } }