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arXiv · 2509.20999

A Simplified Proof for the Edge-Density of 4-Planar Graphs

Aaron Büngener
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Abstract

A graph on $n \ge 3$ vertices drawn in the plane such that each edge is crossed at most four times has at most $6(n-2)$ edges -- this result, proven by Ackerman, is outstanding in the literature of beyond-planar graphs with regard to its tightness and the structural complexity of the graph class. We provide a much shorter proof while at the same time relaxing the conditions on the graph and its embedding, i.e., allowing multi-edges and non-simple drawings.

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Aaron Büngener. 2026-06-11. A Simplified Proof for the Edge-Density of 4-Planar Graphs. https://arxiv.org/abs/2509.20999

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