English

Maximizing five-cycles in $K_r$-free graphs

Combinatorics 2022-05-03 v3

Abstract

The Erd\H{o}s Pentagon problem asks to find an nn-vertex triangle-free graph that is maximizing the number of 55-cycles. The problem was solved using flag algebras by Grzesik and independently by Hatami, Hladk\'{y}, Kr\'{a}l', Norin, and Razborov. Recently, Palmer suggested the general problem of maximizing the number of 55-cycles in Kk+1K_{k+1}-free graphs. Using flag algebras, we show that every Kk+1K_{k+1}-free graph of order nn contains at most 110k4(k45k3+10k210k+4)n5+o(n5)\frac{1}{10k^4}(k^4 - 5k^3 + 10k^2 - 10k + 4)n^5 + o(n^5) copies of C5C_5 for any k3k \geq 3, with the Tur\'an graph begin the extremal graph for large enough nn.

Keywords

Cite

@article{arxiv.2007.03064,
  title  = {Maximizing five-cycles in $K_r$-free graphs},
  author = {Bernard Lidický and Kyle Murphy},
  journal= {arXiv preprint arXiv:2007.03064},
  year   = {2022}
}

Comments

26 pages

R2 v1 2026-06-23T16:53:58.557Z