Hedetniemi's conjecture and fiber products of graphs
Claude Tardif, Imed Zaguia · 2011
We prove that for n 4, a fiber product of n-chromatic graphs over n-colourings can have chromatic number strictly less than n. This refutes a conjecture of Y. Carbonneaux, S. Gravier, A. Khelladi, A. Semri, Coloring fiber product of graphs. AKCE Int. J. Graphs Comb. 3 (2006), 59‐64.