
doi: 10.37236/5418
We consider circular version of the famous Nelson-Hadwiger problem. It is know that 4 colors are necessary and 7 colors suffice to color the euclidean plane in such a way that points at distance one get different colors. In $r$-circular coloring we assign arcs of length one of a circle with a perimeter $r$ in such a way that points at distance one get disjoint arcs. In this paper we show the existence of $r$-circular coloring for $r=4+\frac{4\sqrt{3}}{3}\approx 6.30$. It is the first result with $r$-circular coloring of the plane with $r$ smaller than 7. We also show $r$-circular coloring of the plane with $r<7$ in the case when we require disjoint arcs for points at distance belonging to the internal [0.9327,1.0673].
Coloring of graphs and hypergraphs, Graph representations (geometric and intersection representations, etc.), coloring of the plane, Hadwiger-Nelson problem, circular colouring, Planar graphs; geometric and topological aspects of graph theory
Coloring of graphs and hypergraphs, Graph representations (geometric and intersection representations, etc.), coloring of the plane, Hadwiger-Nelson problem, circular colouring, Planar graphs; geometric and topological aspects of graph theory
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