Abstract
According to the Erdős–Szekeres theorem, for every n, a sufficiently large set of points in general position in the plane contains n in convex position. In this note we investigate the line version of this result, that is, we want to find n lines in convex position in a sufficiently large set of lines that are in general position. We prove almost matching upper and lower bounds for the minimum size of the set of lines in general position that always contains n in convex position. This is quite unexpected, since in the case of points, the best known bounds are very far from each other. We also establish the dual versions of many variants and generalizations of the Erdős–Szekeres theorem.
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Acknowledgments
Research of the first and second authors was partially supported by ERC Advanced Research Grant No. 267165 (DISCONV), and research of the first and third authors by Hungarian Science Foundation Grant OTKA K 83767 and K 111827. Research of the third author was also supported by Hungarian Science Foundation Grant OTKA NN 102029 under the EuroGIGA programs ComPoSe and GraDR. We would like to thank Miguel Raggi who offered to write the program that determined the value of \({\text {ES}}_l(5)\).
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Bárány, I., Roldán-Pensado, E. & Tóth, G. Erdős–Szekeres Theorem for Lines. Discrete Comput Geom 54, 669–685 (2015). https://doi.org/10.1007/s00454-015-9705-y
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DOI: https://doi.org/10.1007/s00454-015-9705-y