A 4-choosable graph that is not (8 : 2)-choosable
Résumé
In 1980, Erdős, Rubin and Taylor asked whether for all positive integers a, b, and m, every (a : b)-choosable graph is also (am : bm)-choosable. We provide a negative answer by exhibiting a 4-choosable graph that is not (8 : 2)-choosable.
Origine : Publication financée par une institution
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