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arXiv · 1702.07555

A generalization of crossing families

Patrick Schnider
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Abstract

For a set of points in the plane, a \emph{crossing family} is a set of line segments, each joining two of the points, such that any two line segments cross. We investigate the following generalization of crossing families: a \emph{spoke set} is a set of lines drawn through a point set such that each unbounded region of the induced line arrangement contains at least one point of the point set. We show that every point set has a spoke set of size $\sqrt{\frac{n}{8}}$. We also characterize the matchings obtained by selecting exactly one point in each unbounded region and connecting every such point to the point in the antipodal unbounded region.

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Patrick Schnider. 2017-02-24. A generalization of crossing families. https://arxiv.org/abs/1702.07555

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