Abstract
A biased graph is a graph with a distinguished set of circles, such that if two circles in the set are contained in a theta graph, then so is the third circle of the theta graph. We introduce a new biased graph, a biased expansion of a biased graph, that satisfies certain lifting and projection properties with the original biased graph. We relate the chromatic polynomials of a biased graph and its biased expansions, thus generalizing a biased-graph result of Zaslavsky [7] and a hyperplane result of Ehrenborg and Readdy [1]. We also determine which biased expansions have supersolvable bias matroids.
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Koban, L. Biased Expansions of Biased Graphs and Their Chromatic Polynomials. Ann. Comb. 16, 781–788 (2012). https://doi.org/10.1007/s00026-012-0160-7
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DOI: https://doi.org/10.1007/s00026-012-0160-7