English

Large subgraphs in pseudo-random graphs

Probability 2016-10-13 v1 Combinatorics

Abstract

We consider classes of pseudo-random graphs on nn vertices for which the degree of every vertex and the co-degree between every pair of vertices are in the intervals (npCnδ,np+Cnδ)(np - Cn^\delta,np+Cn^\delta) and (np2Cnδ,np2+Cnδ)(np^2- C n^\delta, np^2 +C n^\delta) respectively, for some absolute constant CC, and p,δ(0,1)p, \delta \in (0,1). We show that for such pseudo-random graphs the number of induced isomorphic copies of subgraphs of size ss are approximately same as that of an Erd\H{o}s-R\'{e}yni random graph with edge connectivity probability pp as long as s(((1δ)12)o(1))logn/log(1/p)s \le (((1-\delta)\wedge \frac{1}{2})-o(1))\log n/\log (1/p), when p(0,1/2]p \in (0,1/2]. When p(1/2,1)p \in (1/2,1) we obtain a similar result. Our result is applicable for a large class of random and deterministic graphs including exponential random graph models (ERGMs), thresholded graphs from high-dimensional correlation networks, Erd\H{o}s-R\'{e}yni random graphs conditioned on large cliques, random dd-regular graphs and graphs obtained from vector spaces over binary fields. In the context of the last example, the results obtained are optimal. Straight-forward extensions using the proof techniques in this paper imply strengthening of the above results in the context of larger motifs if a model allows control over higher co-degree type functionals.

Keywords

Cite

@article{arxiv.1610.03762,
  title  = {Large subgraphs in pseudo-random graphs},
  author = {Anirban Basak and Shankar Bhamidi and Suman Chakraborty and Andrew Nobel},
  journal= {arXiv preprint arXiv:1610.03762},
  year   = {2016}
}

Comments

52 pages

R2 v1 2026-06-22T16:18:53.666Z