Abstract
We prove two theorems concerning incidence posets of graphs, cover graphs of posets and a related graph parameter. First, answering a question of Haxell, we show that the chromatic number of a graph is not bounded in terms of the dimension of its incidence poset, provided the dimension is at least four. Second, answering a question of Kříž and Nešetřil, we show that there are graphs with large girth and large chromatic number among the class of graphs having eye parameter at most two.
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Trotter, W.T., Wang, R. Incidence Posets and Cover Graphs. Order 31, 279–287 (2014). https://doi.org/10.1007/s11083-013-9301-9
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DOI: https://doi.org/10.1007/s11083-013-9301-9