Square coloring planar graphs with automatic discharging

04/12/2022

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by   Nicolas Bousquet, et al.

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The discharging method is a powerful proof technique, especially for graph coloring problems. Its major downside is that it often requires lengthy case analyses, which are sometimes given to a computer for verification. However, it is much less common to use a computer to actively look for a discharging proof. In this paper, we use a Linear Programming approach to automatically look for a discharging proof. While our system is not entirely autonomous, we manage to make some progress towards Wegner's conjecture for distance-2 coloring of planar graphs, by showing that 12 colors are sufficient to color at distance 2 every planar graph with maximum degree 4.