Let G be a graph and let V(G) be the vertex set of G. Define the neighborhood complex N(G) as the simplicial complex whose simplices are those subsets of V(G) which have a common neighbor.

一个图G的邻域复形是以G的顶点为顶点，以G的具有公共邻接顶点的顶点子集为单形的抽象复形。

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