Toughness of graphs and the existence of factors
β Scribed by P. Katerinis
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 643 KB
- Volume
- 80
- Category
- Article
- ISSN
- 0012-365X
No coin nor oath required. For personal study only.
β¦ Synopsis
Theorem 2. Let G be a 2-tough graph. Then for any function f : V(G)+ { 1, 2) such that C xsvCcj f (x) in euen, G has an f-factor.
Before stating the second main theorem of this paper it is necessary to make the following definition.
Let G be a graph and let g and f be two integer-valued functions defined on
such that g(x) Sf (x) f or all x E V(G). Then a [g, f]-factor of G is a
π SIMILAR VOLUMES
In a paper with the same title (Enomoto et al., 1985) we proved Chv&al's conjecture that ktough graphs have k-factors if they satisfy trivial necessary conditions. In this paper, we introduce a variation of toughness, and prove a stronger result for the existence of l-or 2-factors. This solves a con
## Abstract Degree conditions on the vertices of a __t__βtough graph __G__(1 β¦ __t__ β¦ 2) that ensure the existence of a 2βfactor in __G__ are presented. These conditions are asymptotically best possible for every __t__ Ο΅ [1, 3/2] and for infinitely many __t__ Ο΅ [3/2, 2].
## Abstract We give examples of edgeβchromatic critical graphs __G__ of the following types: (i) of even order and having no 1βfactor, and (ii) of odd order and having a vertex __v__ of minimum degree such that __G__ β __v__ has no 1βfactor. The first disproves a conjecture of S. Fiorini and R. J.
In this short note we argue that the toughness of split graphs can be computed in polynomial time.
In this paper we use Tutte's f-factor theorem and the method of amalgamations to find necessary and sufficient conditions for the existence of a k-factor in the complete multipartite graph K(p(1 ) ..... p(n)), conditions that are reminiscent of the Erd6s-Gallai conditions for the existence of simple