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The Crossing Number of Seq-Shellable Drawings of Complete Graphs - MaRDI portal

The Crossing Number of Seq-Shellable Drawings of Complete Graphs

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Publication:6299330

DOI10.1007/978-3-319-94667-2_23arXiv1803.07515MaRDI QIDQ6299330

Petra Mutzel, Lutz Oettershagen

Publication date: 20 March 2018

Abstract: The Harary-Hill conjecture states that for every n>0 the complete graph on n vertices Kn, the minimum number of crossings over all its possible drawings equals �egin{align*} H(n) := frac{1}{4}Biglfloorfrac{n}{2}Big floorBiglfloorfrac{n-1}{2}Big floorBiglfloorfrac{n-2}{2}Big floorBiglfloorfrac{n-3}{2}Big floor ext{.} end{align*} So far, the lower bound of the conjecture could only be verified for arbitrary drawings of Kn with nleq12. In recent years, progress has been made in verifying the conjecture for certain classes of drawings, for example 2-page-book, x-monotone, x-bounded, shellable and bishellable drawings. Up to now, the class of bishellable drawings was the broadest class for which the Harary-Hill conjecture has been verified, as it contains all beforehand mentioned classes. In this work, we introduce the class of seq-shellable drawings and verify the Harary-Hill conjecture for this new class. We show that bishellability implies seq-shellability and exhibit a non-bishellable but seq-shellable drawing of K11, therefore the class of seq-shellable drawings strictly contains the class of bishellable drawings.












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