Burling graphs revisited, part III: Applications to χ-boundedness
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The Burling sequence is a sequence of triangle-free graphs of unbounded chromatic number. The class of Burling graphs consists of all the induced subgraphs of the graphs of this sequence. In the first and second parts of this work, we introduced derived graphs, a class of graphs, equal to the class of Burling graphs, and proved several geometric and structural results about them. In this third part, we use those results to find some Burling and non-Burling graphs, and we see some applications of this in the theory of χ-boundedness. In particular, we show that several graphs, like K_5, some series-parallel graphs that we call necklaces, and some other graphs are not weakly pervasive.
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