{ "id": "1206.1016", "version": "v1", "published": "2012-06-05T18:27:31.000Z", "updated": "2012-06-05T18:27:31.000Z", "title": "Mantel's Theorem for random graphs", "authors": [ "Bobby DeMarco", "Jeff Kahn" ], "comment": "15 pages", "categories": [ "math.PR", "cs.DM", "math.CO" ], "abstract": "For a graph $G$, denote by $t(G)$ (resp. $b(G)$) the maximum size of a triangle-free (resp. bipartite) subgraph of $G$. Of course $t(G) \\geq b(G)$ for any $G$, and a classic result of Mantel from 1907 (the first case of Tur\\'an's Theorem) says that equality holds for complete graphs. A natural question, first considered by Babai, Simonovits and Spencer about 20 years ago is, when (i.e. for what $p=p(n)$) is the \"Erd\\H{o}s-R\\'enyi\" random graph $G=G(n,p)$ likely to satisfy $t(G) = b(G)$? We show that this is true if $p>C n^{-1/2} \\log^{1/2}n $ for a suitable constant $C$, which is best possible up to the value of $C$.", "revisions": [ { "version": "v1", "updated": "2012-06-05T18:27:31.000Z" } ], "analyses": { "subjects": [ "05D40", "05C35", "05C80" ], "keywords": [ "random graph", "mantels theorem", "natural question", "complete graphs", "equality holds" ], "note": { "typesetting": "TeX", "pages": 15, "language": "en", "license": "arXiv", "status": "editable", "adsabs": "2012arXiv1206.1016D" } } }