English

The neighborhood complex of a random graph

Combinatorics 2010-09-23 v4 Algebraic Topology

Abstract

For a graph G, the neighborhood complex N[G] is the simplicial complex having all subsets of vertices with a common neighbor as its faces. It is a well known result of Lovasz that if N[G] is k-connected, then the chromatic number of G is at least k + 3. We prove that the connectivity of the neighborhood complex of a random graph is tightly concentrated, almost always between 1/2 and 2/3 of the expected clique number. We also show that the number of dimensions of nontrivial homology is almost always small, O(log d), compared to the expected dimension d of the complex itself.

Keywords

Cite

@article{arxiv.math/0512077,
  title  = {The neighborhood complex of a random graph},
  author = {Matthew Kahle},
  journal= {arXiv preprint arXiv:math/0512077},
  year   = {2010}
}

Comments

9 pages; stated theorems more clearly and slightly generalized, and fixed one or two typos

R2 v1 2026-07-22T17:28:14.592Z