A note on the Krausz theorem and the Whitney theorem for mixed line graphs

Abstract

A mixed line graph of a mixed graph generalizes the notion of a line graph of an ordinary graph. The Krausz theorem on covering characterization of line graphs and a restricted variant of the Whitney theorem on isomorphism are formulated and proved in the framework of mixed line graphs. Moreover, we extend the notion of a mixed graph by allowing the existence of edges that are oriented away from each of their ends. The mentioned theorems are formulated and proved in this setting, as well.