English

Enhancing the Erd\H{o}s-Lov\'asz Tihany Conjecture for graphs with independence number two

Combinatorics 2020-08-19 v1

Abstract

Let s2s\ge2 and t2t\ge2 be integers. A graph GG is (s,t)(s,t)-\emph{splittable} if V(G)V(G) can be partitioned into two sets SS and TT such that χ(G[S])s\chi(G[S])\geq s and χ(G[T])t\chi(G[T])\geq t. The well-known Erd\H{o}s-Lov\'asz Tihany Conjecture from 1968 states that every graph GG whose chromatic number χ(G)=s+t1\chi(G)=s+t-1 is more than its clique number ω(G)\omega(G) is (s,t)(s,t)-splittable. In this paper, we prove an enhanced version of the Erd\H{o}s-Lov\'asz Tihany Conjecture for graphs with independence number two. That is, for every graph GG with χ(G)=s+t1>ω(G)+1\chi(G)=s+t-1>\omega(G)+1 is (s,t+1)(s,t+1)-splittable. There are examples showing that this result is best possible.

Keywords

Cite

@article{arxiv.2008.08017,
  title  = {Enhancing the Erd\H{o}s-Lov\'asz Tihany Conjecture for graphs with independence number two},
  author = {Yue Wang and Gexin Yu},
  journal= {arXiv preprint arXiv:2008.08017},
  year   = {2020}
}