We show that, if an n-vertex triangulation T of maximum degree Delta has a dual that contains a cycle of length l, then T has a non-crossing straight-line drawing in which some set, called a collinear set, of Omega(l/Delta^4) vertices lie on a line. Using the current lower bounds on the length of longest cycles in 3-regular 3-connected graphs, this implies that every n-vertex planar graph of maximum degree Delta has a collinear set of size Omega(n^{0.8}/Delta^4). Very recently, Dujmović et al. (SODA 2019) showed that, if S is a collinear set in a triangulation T then, for any point set X subset R^2 with |X|=|S|, T has a non-crossing straight-line drawing in which the vertices of S are drawn on the points in X. Because of this, collinear sets have numerous applications in graph drawing and related areas.
@InProceedings{dujmovic_et_al:LIPIcs.SoCG.2019.29, author = {Dujmovi\'{c}, Vida and Morin, Pat}, title = {{Dual Circumference and Collinear Sets}}, booktitle = {35th International Symposium on Computational Geometry (SoCG 2019)}, pages = {29:1--29:17}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-104-7}, ISSN = {1868-8969}, year = {2019}, volume = {129}, editor = {Barequet, Gill and Wang, Yusu}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2019.29}, URN = {urn:nbn:de:0030-drops-104338}, doi = {10.4230/LIPIcs.SoCG.2019.29}, annote = {Keywords: Planar graphs, collinear sets, untangling, column planarity, universal point subsets, partial simultaneous geometric drawings} }
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