English

Maximizing subgraph density in graphs of bounded degree and clique number

Combinatorics 2025-08-18 v2

Abstract

We asymptotically determine the maximum density of subgraphs isomorphic to HH, where HH is any graph containing a dominating vertex, in graphs GG on nn vertices with bounded maximum degree and bounded clique number. That is, we asymptotically determine the constant c=c(H,Δ,ω)c=c(H,\Delta,\omega) such that ex(n,H,{K1,Δ+1,Kω+1})=(1on(1))cn(n,H,\{K_{1,\Delta+1},K_{\omega+1}\})=(1-o_n(1))cn where ω\omega is sufficiently large. Following recent interest in the corresponding parameter mex(m,H,F)(m,H,F) where where we fix the number of edges mm instead of the number of vertices nn of the graph, we determine the asymptotics of mex(m,H,{K1,1,Δ+1,Kω+1})(m,H,\{K_{1,1,\Delta+1},K_{\omega+1}\}) when HH has at least two dominating vertices. We obtain these results via a uniform proof of a common technical generalization of both, where we fix the number of uu-cliques in the graph. This general result may be of independent interest. Then we localize these results, proving a tight inequality involving the sizes of the locally largest cliques and complete split graphs.

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Cite

@article{arxiv.2504.10290,
  title  = {Maximizing subgraph density in graphs of bounded degree and clique number},
  author = {Rachel Kirsch},
  journal= {arXiv preprint arXiv:2504.10290},
  year   = {2025}
}

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16 pages