## Abstract A graph with __n__ vertices that contains no triangle and no 5‐cycle and minimum degree exceeding __n__/4 contains an independent set with at least (3__n__)/7 vertices. This is best possible. The proof proceeds by producing a homomorphism to the 7‐cycle and invoking the No Homomorphism
Homomorphisms of 3-chromatic graphs
✍ Scribed by Michael O Albertson; Karen L Collins
- Publisher
- Elsevier Science
- Year
- 1985
- Tongue
- English
- Weight
- 411 KB
- Volume
- 54
- Category
- Article
- ISSN
- 0012-365X
No coin nor oath required. For personal study only.
📜 SIMILAR VOLUMES
A fold is a sequence of simple folds (elementary homomorphisms in which the identified vertices are both adjacent to a common vertex). It was shown in (C. R. Cook and A. B. Evans, Graph folding. Proceedings o f the South Eastern Conference on Combinatorics, Graph Theory, and Computing, Boca Raton, 1
This note characterizes graphs with the second term of their chitimatic diherence seq-uences equal t-o& \*d gives a r! 2% of graphs, called Isi',, that are determined by their chromatic difference sequences. It also gives a large class of n-chromatic graphs for which \V, is a homomorphic image. It i
## Abstract We answer two open questions posed by Cameron and Nesetril concerning homomorphism–homogeneous graphs. In particular we show, by giving a characterization of these graphs, that extendability to monomorphism or to homomorphism leads to the same class of graphs when defining homomorphism–
## Abstract A __geometric graph__ is a simple graph drawn on points in the plane, in general position, with straightline edges. A __geometric__ __homomorphism__ from to is a vertex map that preserves adjacencies and crossings. This work proves some basic properties of geometric homomorphisms and