Hadwiger conjecture (graph theory)

The Hadwiger conjecture is a significant open problem in graph theory, proposed by Hugo Hadwiger in 1943. It asserts that if a graph \( G \) cannot be mapped onto the complete graph \( K_{t+1} \) (which means that \( G \) does not contain \( K_{t+1} \) as a minor), then the chromatic number \( \chi(G) \) of the graph is at most \( t \).