{ "id": "1110.4205", "version": "v1", "published": "2011-10-19T08:30:27.000Z", "updated": "2011-10-19T08:30:27.000Z", "title": "A Tur'an-type problem for circular arc graphs", "authors": [ "Rosalie Carlson", "Stephen Flood", "Kevin O'Neill", "Francis Edward Su" ], "comment": "18 pages, 8 figures, related papers at http://www.math.hmc.edu/~su/papers.html", "categories": [ "math.CO", "cs.DM" ], "abstract": "A circular arc graph is the intersection graph of a collection of connected arcs on the circle. We solve a Tur'an-type problem for circular arc graphs: for n arcs, if m and M are the minimum and maximum number of arcs that contain a common point, what is the maximum number of edges the circular arc graph can contain? We establish a sharp bound and produce a maximal construction. For a fixed m, this can be used to show that if the circular arc graph has enough edges, there must be a point that is covered by at least M arcs. In the case m=0, we recover results for interval graphs established by Abbott and Katchalski (1979). We suggest applications to voting situations with interval or circular political spectra.", "revisions": [ { "version": "v1", "updated": "2011-10-19T08:30:27.000Z" } ], "analyses": { "subjects": [ "05C75", "91B12" ], "keywords": [ "circular arc graph", "turan-type problem", "maximum number", "intersection graph", "interval graphs" ], "note": { "typesetting": "TeX", "pages": 18, "language": "en", "license": "arXiv", "status": "editable", "adsabs": "2011arXiv1110.4205C" } } }