English

Extremal problems for a matching and any other graph

Combinatorics 2023-07-25 v1

Abstract

For a family of graphs \F\F, a graph is called \F\F-free if it does not contain any member of \F\F as a subgraph. The generalized Tur\'an number \ex(n,Kr,\F)\ex(n,K_r,\F) is the maximum number of KrK_r in an nn-vertex \F\F-free graph and \ex(n,K2,\F)=\ex(n,\F)\ex(n,K_2,\F)=\ex(n,\F), i.e., the classical Tur\'an number. Let Ms+1M_{s+1} be a matching on s+1s+1 edges and FF be any graph. In this paper, we determine \ex(n,Kr,{Ms+1,F})\ex(n,K_r, \{M_{s+1},F\}) apart from a constant additive term and also give a condition when the error constant term can be determined. In particular, we give the exact value of \ex(n,{Ms+1,F})\ex(n,\{M_{s+1},F\}) for FF being any non-bipartite graph or some bipartite graphs. Furthermore, we determine \ex(n,Kr,{Ms+1,F})\ex(n,K_r,\{M_{s+1},F\}) when FF is color critical with χ(F)max{r+1,4}\chi(F)\ge \max\{r+1,4\}. These extend the results in [2,11,18].

Keywords

Cite

@article{arxiv.2307.11983,
  title  = {Extremal problems for a matching and any other graph},
  author = {Xiutao Zhu and Yaojun Chen},
  journal= {arXiv preprint arXiv:2307.11983},
  year   = {2023}
}
R2 v1 2026-06-28T11:37:31.717Z