Roman Domination in Weighted Graphs

A Roman dominating function for a (non-weighted) graph G=(V,E) is a function f:V→{0,1,2} such that every vertex u∈V with f(u)=0 has at least one neighbor v∈V such that f(v)=2. The minimum weight ∑v∈Vf(v) of a Roman dominating function f on G is called the Roman domination number of G and is denoted by γR(G). A graph G=(V,E), together with a positive real-valued weight-function w:V→R>0, is called a weighted graph and is denoted by (G;w). The minimum weight ∑v∈Vf(v)w(v) of a Roman dominating function f on G is called the weighted Roman domination number of G and is denoted by γwR(G). The domination and Roman domination numbers of unweighted graphs have been extensively studied, particularly for their applications in bioinformatics and computational biology. However, graphs used to model biomolecular structures often require weights to be biologically meaningful. In this paper, we initiate the study of the weighted Roman domination number in weighted graphs. We first establish several bounds for this parameter and present various realizability results. Furthermore, we determine the exact values for several well-known graph families and demonstrate an equivalence between the weighted Roman domination number and the differential of a weighted graph.