Abstract
The bull is a graph consisting of a triangle and two pendant edges. A graphs is called bull-free if no induced subgraph of it is a bull. In this paper we prove that every bull-free graph on n vertices contains either a clique or a stable set of size nfrac(1, 4), thus settling the Erdo{combining double acute accent}s-Hajnal conjecture [P. Erdo{combining double acute accent}s, A. Hajnal, Ramsey-type theorems, Discrete Appl. Math. 25 (1989) 37-52] for the bull.
Original language | English |
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Pages (from-to) | 1301-1310 |
Number of pages | 10 |
Journal | Journal of Combinatorial Theory. Series B |
Volume | 98 |
Issue number | 6 |
DOIs | |
State | Published - Nov 2008 |
Keywords
- Bull-free graphs
- Clique
- Induced subgraphs
- Stable set