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The Petersen colouring conjecture

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Posed by François Jaeger · 1988 · Graph theory · ~1 min read · difficulty 5/5

graph-theory cubic-graphs

The problem

Every bridgeless cubic graph admits a normal edge-mapping into the Petersen graph (a Petersen colouring).

History & significance

Jaeger (1988) proposed the Petersen graph as a universal target for bridgeless cubic graphs — a common roof over the cycle double cover, Berge–Fulkerson, and five-flow conjectures, since a Petersen colouring implies all three. Partial results cover large girth and planar cases; the general statement is wide open, and its position as the strongest of the cubic-graph conjectures makes it the natural summit: prove Petersen colouring and three famous problems fall at once.

Still open.

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