English

Erd\H{o}s-Lov\'asz Tihany Conjecture for graphs with forbidden holes

Combinatorics 2018-05-30 v1

Abstract

A hole in a graph is an induced cycle of length at least 44. Let s2s\ge2 and t2t\ge2 be integers. A graph GG is (s,t)(s,t)-splittable if V(G)V(G) can be partitioned into two sets SS and TT such that χ(G[S])s\chi(G[S ]) \ge s and χ(G[T])t\chi(G[T ]) \ge t. The well-known Erd\H{o}s-Lov\'asz Tihany Conjecture from 1968 states that every graph GG with ω(G)<χ(G)=s+t1\omega(G) < \chi(G) = s + t - 1 is (s,t)(s,t)-splittable. This conjecture is hard, and few related results are known. However, it has been verified to be true for line graphs, quasi-line graphs, and graphs with independence number 22. In this paper, we establish more evidence for the Erd\H{o}s-Lov\'asz Tihany Conjecture by showing that every graph GG with α(G)3\alpha(G)\ge3, ω(G)<χ(G)=s+t1\omega(G) < \chi(G) = s + t - 1, and no hole of length between 44 and 2α(G)12\alpha(G)-1 is (s,t)(s,t)-splittable, where α(G)\alpha(G) denotes the independence number of a graph GG.

Keywords

Cite

@article{arxiv.1805.11437,
  title  = {Erd\H{o}s-Lov\'asz Tihany Conjecture for graphs with forbidden holes},
  author = {Zi-Xia Song},
  journal= {arXiv preprint arXiv:1805.11437},
  year   = {2018}
}

Comments

arXiv admin note: text overlap with arXiv:1607.06718, arXiv:1610.00636