文摘
Hajós conjectured that graphs containing no subdivision of \(K_5\) are 4-colorable. It is shown in Yu and Zickfeld (J Comb Theory Ser B 96:482–492, 2006) that if there is a counterexample to this conjecture then any minimum such counterexample must be 4-connected. In this paper, we further show that if \(G\) is a minimum counterexample to Hajós’ conjecture and \(S\) is a 4-cut in \(G\) then \(G-S\) has exactly two components. Keywords Coloring Subdivision of graph Independent paths Planar graph