The problem on a quadratic lattice embedded on the torus is considered here.In 1991, Thomassen characterized that there only two types of quadrilateral latt
A vertex-colored graph is rainbow vertex-connected if any two vertices are connected by a path whose internal vertices have distinct colors.The rainbow vert
Let G be a simple graph.The matrix Q(G) =D(G) + A(G) denotes the signless Laplacian matrix of G, where D(G) and A(G) denote the diagonal matrix of vertex de
Two chains in a ranked poset P are nested if they are saturated and if the chain containing the element of least rank in their union also contains the eleme