The neighborhood complex 
of a locally finite
graph 
is defined as the abstract simplicial complex formed by the subsets of the neighborhoods
of all vertices of 
.
Neighborhood Complex
See also
NeighborhoodThis entry contributed by Margherita Barile
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References
Arenas, F. G. and Puertas, M. L. "The Neighborhood Complex of an Infinite Graph." Divulgaciones Matemáticas 8, 69-74, 2000.Lovász, L. "Kneser's Conjecture, Chromatic Numbers and Homotopy." J. Comb. Th. A 25, 319-324, 1978.Referenced on Wolfram|Alpha
Neighborhood ComplexCite this as:
Barile, Margherita. "Neighborhood Complex." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/NeighborhoodComplex.html