2017/03/01 by L. Sunil Chandran, Anita Das, Chandran, L. Sunil +5
Computer Science · Mathematics · #Advanced Graph Theory Research #Bounded function #Bounding overwatch #Combinatorics #Combinatorics (math.CO) #Complete coloring #Computer science #Data Structures and Algorithms (cs.DS) #Discrete mathematics #Edge coloring #FOS: Computer and information sciences #FOS: Mathematics #Fractional coloring #Graph #Graph Labeling and Dimension Problems #Graph coloring #Graph power #Line graph #Mathematics #Pathwidth #Time complexity #Treewidth #cs.DS #math.CO
paper · pdf · doi:10.48550/arxiv.1703.00236
published in arXiv (Cornell University) (Cornell University)
openalex publication_date 2017/03/01 · arxiv created 2018/01/16 · arxiv updated 2018/01/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A well-studied coloring problem is to assign colors to the edges of a graph G so that, for every pair of vertices, all edges of at least one shortest path between them receive different colors. The minimum number of colors necessary in such a coloring is the strong rainbow connection number (\src(G)) of the graph. When proving upper bounds on \src(G), it is natural to prove that a coloring exists where, for every shortest path between every pair of vertices in the graph, all edges of the path receive different colors. Therefore, we introduce and formally define this more restricted edge coloring number, which we call very strong rainbow connection number (\vsrc(G)). In this paper, we give upper bounds on \vsrc(G) for several graph classes, some of which are tight. These immediately imply new upper bounds on \src(G) for these classes, showing that the study of \vsrc(G) enables meaningful progress on bounding \src(G). Then we study the complexity of the problem to compute \vsrc(G), particularly for graphs of bounded treewidth, and show this is an interesting problem in its own right. We prove that \vsrc(G) can be computed in polynomial time on cactus graphs; in contrast, this question is still open for \src(G). We also observe that deciding whether \vsrc(G) = k is fixed-parameter tractable in k and the treewidth of G. Finally, on general graphs, we prove that there is no polynomial-time algorithm to decide whether \vsrc(G) ≤ 3 nor to approximate \vsrc(G) within a factor n1-ε, unless P=NP.