## dedicated to professor w. t. tutte on the occasion of his eightieth birtday It is known that the chromatic number of a graph G=(V, E) with V= [1, 2, ..., n] exceeds k iff the graph polynomial f G => ij # E, i<j (x i &x j ) lies in certain ideals. We describe a short proof of this result, using
On generalized graph colorings
β Scribed by Jason I. Brown; Derek G. Corneil
- Publisher
- John Wiley and Sons
- Year
- 1987
- Tongue
- English
- Weight
- 610 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0364-9024
No coin nor oath required. For personal study only.
β¦ Synopsis
Given a property P, graph G. and k 2 0, a P k-coloring is a function 7r: V(G) + { I , ... , k) such that the subgraph induced by each color class has property P; x ( G : P ) is the least k, for which G has a P k-coloring. We investigate here the theory of P colorings. Generalizations of the wellknown notions of vertex criticality and unique colorability are discussed, and w e extend a theorem of Erdos to Pchromatic graphs.
NOTATION AND BACKGROUND
In this paper, all graphs are finite, undirected, and without loops or multiple edges, and isomorphic graphs will be considered identical. The term subgraph will always stand for "induced subgraph" and we write H A G to denote H is a subgraph of G; for U V ( G ) , (U)c (or ( U ) if no ambiguity arises) denotes the subgraph of G induced by U . Unless otherwise stated, different graphs are assumed to be disjoint. The parameters a, w , y , and x denote, respectively, the independence number, the clique number, the girth, and the chromatic number. For other standard notation, we follow [ I ) .
Let G denote the set of all graphs. A subset P of G is a property iff KO, K , E
π SIMILAR VOLUMES
Suppose /(G)=r and P V(G). It is known that if the distance between any two vertices in P is at least 4, then any (r+1)-coloring of P extends to an (r+1)-coloring of all of G, but an r-coloring of P might not extend to an r-coloring of G. We show that if the distance between any two vertices in P is
Bounds are given on the number of colors required to color the edges of a graph (multigraph) such that each color appears at each vertex u at most m(u) times. The known results and proofs generalize in natural ways. Certain new edge-coloring problems, which have no counterparts when m(u) = 1 for all
## Abstract We investigate bounds on the chromatic number of a graph __G__ derived from the nonexistence of homomorphisms from some path \documentclass{article}\footskip=0pc\pagestyle{empty}\begin{document}\begin{eqnarray\*}\vec{P}\end{eqnarray\*}\end{document} into some orientation \documentclass{
## Abstract It is well known that every planar graph __G__ is 2βcolorable in such a way that no 3βcycle of __G__ is monochromatic. In this paper, we prove that __G__ has a 2βcoloring such that no cycle of length 3 or 4 is monochromatic. The complete graph __K__~5~ does not admit such a coloring. On