{ "id": "1009.4736", "version": "v2", "published": "2010-09-23T23:07:53.000Z", "updated": "2011-03-29T01:44:44.000Z", "title": "Point sets that minimize $(\\le k)$-edges, 3-decomposable drawings, and the rectilinear crossing number of $K_{30}$", "authors": [ "M. Cetina", "C. Hernández-Vélez", "J. Leaños", "C. Villalobos" ], "comment": "14 pages", "doi": "10.1016/j.disc.2011.03.030", "categories": [ "math.CO" ], "abstract": "There are two properties shared by all known crossing-minimizing geometric drawings of $K_n$, for $n$ a multiple of 3. First, the underlying $n$-point set of these drawings has exactly $3\\binom{k+2}{2}$ $(\\le k)$-edges, for all $0\\le k < n/3$. Second, all such drawings have the $n$ points divided into three groups of equal size; this last property is captured under the concept of 3-decomposability. In this paper we show that these properties are tightly related: every $n$-point set with exactly $3\\binom{k+2}{2}$ $(\\le k)$-edges for all $0\\le k < n/3$, is 3-decomposable. As an application, we prove that the rectilinear crossing number of $K_{30}$ is 9726.", "revisions": [ { "version": "v2", "updated": "2011-03-29T01:44:44.000Z" } ], "analyses": { "keywords": [ "rectilinear crossing number", "point set", "crossing-minimizing geometric drawings", "application" ], "tags": [ "journal article" ], "note": { "typesetting": "TeX", "pages": 14, "language": "en", "license": "arXiv", "status": "editable", "adsabs": "2010arXiv1009.4736C" } } }