Edge lifting and Roman domination in graphs
Let [Formula: see text] be a graph, and let [Formula: see text] be an induced path centered at [Formula: see text]. An edge lift defined on [Formula: see text] is the action of removing edges [Formula: see text] and [Formula: see text] while adding the edge [Formula: see text] to the edge set of [Formula: see text]. In this paper, we initiate the study of the effects of edge lifting on the Roman domination number of a graph, where various properties are established. A characterization of all trees for which every edge lift increases the Roman domination number is provided. Moreover, we characterize the edge lift of a graph decreasing the Roman domination number, and we show that there are no graphs with at most one cycle for which every possible edge lift can have this property.