In addition to a widely studied notion of homomorphisms of graphs and hypergraphs, [2, 5 , 6, 7, 9, 13, 141, we introduce the dual notion of cohomomorphisms. We shall concentrate on only a few aapects of these mappings, mostly with regard to intended applications, [lo, 111. Our basic motivation is t
Graph properties and hypergraph colourings
โ Scribed by Jason I. Brown; Derek G. Corneil
- Publisher
- Elsevier Science
- Year
- 1991
- Tongue
- English
- Weight
- 855 KB
- Volume
- 98
- Category
- Article
- ISSN
- 0012-365X
No coin nor oath required. For personal study only.
โฆ Synopsis
Given a graph property P, graph G and integer k 20, a P k-colouring of G is a function Jr:V(G)+ (1,.
. ) k} such that the subgraph induced by each colour class has property P.
When P is closed under induced subgraphs, we can construct a hypergraph HG such that G is P k-colourable iff Hg is k-colourable. This correlation enables us to derive interesting new results in hypergraph chromatic theory from a 'graphic' approach.
In particular, we build vertex critical hypergraphs that are not edge critical, construct uniquely colourable hypergraphs with few edges and find graph-to-hypergraph transformations that preserve chromatic numbers.
๐ SIMILAR VOLUMES
Ftiredi, Z&an, Indecomposable regular graphs and hypergraphs, Discrete Mathematics 101 (1992) 59-64. Let G be a d-regular simple graph with n vertices. Here it is proved that for d > 6 -1, G contains a proper regular spanning subhypergraph. The same statement is proved for multigraphs with d > (n -1
## Abstract The notion of a split coloring of a complete graph was introduced by Erdลs and Gyรกrfรกs [7] as a generalization of split graphs. In this work, we offer an alternate interpretation by comparing such a coloring to the classical Ramsey coloring problem via a twoโround game played against an
Burr recently proved [3] that for positive integers m , , m 2 , . . , , m, and any graph G we have x(G) 5 &, if and only if G can be expressed as the edge disjoint union of subgraphs F, satisfying x(F,) 5 m,. This theorem is generalized to hypergraphs. By suitable interpretations the generalization