English

Extremal graphs for edge blow-up of lollipops

Combinatorics 2022-02-15 v1

Abstract

Given a graph HH and an integer pp (p2p\geq 2), the edge blow-up Hp+1H^{p+1} of HH is the graph obtained from replacing each edge in HH by a clique of order (p+1)(p+1), where the new vertices of the cliques are all distinct. The Tur\'{a}n numbers for edge blow-up of matchings were first studied by Erd\H{o}s and Moon. Very recently some substantial progress of the extremal graphs for Hp+1H^{p+1} of larger pp has been made by Yuan. The range of Tur\'{a}n numbers for edge blow-up of all bipartite graphs when p3p\geq 3 and the exact Tur\'{a}n numbers for edge blow-up of all non-bipartite graphs when pχ(H)+1p\geq \chi(H) +1 has been determined by Yuan (2022), where χ(H)\chi(H) is the chromatic number of HH. A lollipop Ck,  C_{k,\;\ell} is the graph obtained from a cycle CkC_k by appending a path P+1P_{\ell+1} to one of its vertices. In this paper, we consider the extremal graphs for Ck,  p+1C_{k,\;\ell}^{p+1} of the rest cases p=2p=2 and p=3p=3.

Keywords

Cite

@article{arxiv.2202.06249,
  title  = {Extremal graphs for edge blow-up of lollipops},
  author = {Yanni Zhai and Xiying Yuan and Zhenyu Ni},
  journal= {arXiv preprint arXiv:2202.06249},
  year   = {2022}
}