arXiv math/05073462005-07math.ATmath.CO

A short proof of w_1^n(Hom(C_{2r+1}, K_{n+2}))=0 for all n and a graph colouring theorem by Babson and Kozlov

Carsten Schultz

备注：: slight simplification of the proof, updated references

英文摘要：

We show that the n-th power of the first Stiefel-Whitney class of the Z_2-operation on the graph complex Hom(C_{2r+1},K_{n+2})$ is zero, confirming a conjecture by Babson and Kozlov. This proves the strong form of their graph colouring theorem, which they had only proven for odd n. Our proof is also considerably simpler than their proof of the weak form of the theorem, which is also known as the Lovász conjecture.

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