{ "id": "1802.06143", "version": "v1", "published": "2018-02-16T22:02:22.000Z", "updated": "2018-02-16T22:02:22.000Z", "title": "On the Turán density of $\\{1, 3\\}$-Hypergraphs", "authors": [ "Shuliang Bai", "Linyuan Lu" ], "comment": "18 pages", "categories": [ "math.CO" ], "abstract": "In this paper, we consider the Tur\\'an problems on $\\{1,3\\}$-hypergraphs. We prove that a $\\{1, 3\\}$-hypergraph is degenerate if and only if it's $H^{\\{1, 3\\}}_5$-colorable, where $H^{\\{1, 3\\}}_5$ is a hypergraph with vertex set $V=[5]$ and edge set $E=\\{\\{2\\}, \\{3\\}, \\{1, 2, 4\\}, \\{1, 3, 5\\}, \\{1, 4, 5\\}\\}.$ Using this result, we further prove that for any finite set $R$ of distinct positive integers, except the case $R=\\{1, 2\\}$, there always exist non-trivial degenerate $R$-graphs. We also compute the Tur\\'an densities of some small $\\{1,3\\}$-hypergraphs.", "revisions": [ { "version": "v1", "updated": "2018-02-16T22:02:22.000Z" } ], "analyses": { "subjects": [ "05C35", "05C65" ], "keywords": [ "hypergraph", "turán density", "turan problems", "non-trivial degenerate", "edge set" ], "note": { "typesetting": "TeX", "pages": 18, "language": "en", "license": "arXiv", "status": "editable" } } }