We present a family of finite unit-distance graphs in the plane that are not 4-colourable, thereby improving the lower bound of the Hadwiger-Nelson problem. The smallest such graph that we have so far discovered has 1581 vertices.
Linked by 2 identifiable commenters in 2 comments across 2 threads, from Apr 2018 to Jun 2019. Found in 5 HN submissions from Apr 2018 to May 2018. Open submission discussions.
The paper has beautiful illustrations. https://arxiv.org/pdf/1804.02385.pdf Animations showing how the larger graphs are built from smaller graphs would be amazing and illustrative for mortal non-mathematical-geniuses.
Could be but he also published a well-received paper on graph coloring, so at least he's not stupid. https://arxiv.org/abs/1804.02385
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