Let G $G$ be a simple graph with maximum degree Δ ( ) ${\rm{\Delta }}(G)$ and chromatic index χ ′ $\chi ^{\prime} (G)$ . A classical result of Vizing shows that either = (G)={\rm{\Delta or + 1 }}(G)+1$ is called edge- }}$ -critical if connected, − e (G-e)={\rm{\Delta for every ∈ E $e\in E(G)$ an n $n$ -vertex graph. conjectured α $\alpha , the independence number at most 2 $\frac{n}{2}$ The cur...

We investigate the local chromatic number of shift graphs and prove that it is close to their chromatic number. This implies that the gap between the directed local chromatic number of an oriented graph and the local chromatic number of the underlying undirected graph can be arbitrarily large. We also investigate the minimum possible directed local chromatic number of oriented versions of “topo...

The local chromatic number of a graph was introduced in [13]. It is in between the chromatic and fractional chromatic numbers. This motivates the study of the local chromatic number of graphs for which these quantities are far apart. Such graphs include Kneser graphs, their vertex color-critical subgraphs, the stable Kneser (or Schrijver) graphs; Mycielski graphs, and their generalizations; and...

In this paper, the total chromatic number and fractional total chromatic number of circulant graphs are studied. For cubic circulant graphs we give upper bounds on the fractional total chromatic number and for 4-regular circulant graphs we find the total chromatic number for some cases and we give the exact value of the fractional total chromatic number in most cases.