{ "id": "1910.11048", "version": "v1", "published": "2019-10-24T12:22:28.000Z", "updated": "2019-10-24T12:22:28.000Z", "title": "Turán number of bipartite graphs with no $K_{t,t}$", "authors": [ "Benny Sudakov", "István Tomon" ], "comment": "8 pages", "categories": [ "math.CO" ], "abstract": "The extremal number of a graph $H$, denoted by $\\mbox{ex}(n,H)$, is the maximum number of edges in a graph on $n$ vertices that does not contain $H$. The celebrated K\\H{o}v\\'ari-S\\'os-Tur\\'an theorem says that for a complete bipartite graph with parts of size $t\\leq s$ the extremal number is $\\mbox{ex}(K_{s,t})=O(n^{2-1/t})$. It is also known that this bound is sharp if $s>(t-1)!$. In this paper, we prove that if $H$ is a bipartite graph such that all vertices in one of its parts have degree at most $t$, but $H$ contains no copy of $K_{t,t}$, then $\\mbox{ex}(n,H)=o(n^{2-1/t})$. This verifies a conjecture of Conlon, Janzer and Lee.", "revisions": [ { "version": "v1", "updated": "2019-10-24T12:22:28.000Z" } ], "analyses": { "keywords": [ "turán number", "extremal number", "complete bipartite graph", "theorem says", "maximum number" ], "note": { "typesetting": "TeX", "pages": 8, "language": "en", "license": "arXiv", "status": "editable" } } }