English

Triangles in graphs without bipartite suspensions

Combinatorics 2023-03-21 v3

Abstract

Given graphs TT and HH, the generalized Tur\'an number ex(n,T,H)(n,T,H) is the maximum number of copies of TT in an nn-vertex graph with no copies of HH. Alon and Shikhelman, using a result of Erd\H os, determined the asymptotics of ex(n,K3,H)(n,K_3,H) when the chromatic number of HH is greater than 3 and proved several results when HH is bipartite. We consider this problem when HH has chromatic number 3. Even this special case for the following relatively simple 3-chromatic graphs appears to be challenging. The suspension H^\widehat H of a graph HH is the graph obtained from HH by adding a new vertex adjacent to all vertices of HH. We give new upper and lower bounds on ex(n,K3,H^)(n,K_3,\widehat{H}) when HH is a path, even cycle, or complete bipartite graph. One of the main tools we use is the triangle removal lemma, but it is unclear if much stronger statements can be proved without using the removal lemma.

Keywords

Cite

@article{arxiv.2004.11930,
  title  = {Triangles in graphs without bipartite suspensions},
  author = {Dhruv Mubayi and Sayan Mukherjee},
  journal= {arXiv preprint arXiv:2004.11930},
  year   = {2023}
}

Comments

New result about path with 5 edges added, Journal ref added

R2 v1 2026-06-23T15:05:07.377Z