2022/12/14 by Tian, Jing, Klavžar, Sandi · 6 citations
#Combinatorics (math.CO) #FOS: Mathematics
paper · doi:10.48550/arxiv.2212.07193
If G is a graph and X⊆ V(G), then X is a total mutual-visibility set if every pair of vertices x and y of G admits a shortest x,y-path P with V(P) ∩ X ⊆ \x,y\. The cardinality of a largest total mutual-visibility set of G is the total mutual-visibility number μ\rm t(G) of G. Graphs with μ\rm t(G) = 0 are characterized as the graphs in which no vertex is the central vertex of a convex P3. The total mutual-visibility number of Cartesian products is bounded and several exact results proved. For instance, μ\rm t(Kn \square Km) = max\n,m\ and μ\rm t(T \square H) = μ\rm t(T)μ\rm t(H), where T is a tree and H an arbitrary graph. It is also demonstrated that μ\rm t(G \square H) can be arbitrary larger than μ\rm t(G)μ\rm t(H).