We show that under certain conditions the square of the graph obtained by identifying a vertex in two graphs with hamiltonian square is also hamiltonian. Using this result, we prove necessary and sufficient conditions for hamiltonicity of the square of a connected graph such that every vertex of degree at least three in a block graph corresponds to a cut vertex and any two these vertices are at...

A set D ⊆ V of vertices is said to be a (connected) distance k-dominating set of G if the distance between each vertex u ∈ V − D and D is at most k (and D induces a connected graph in G). The minimum cardinality of a (connected) distance k-dominating set in G is the (connected) distance k-domination number of G, denoted by γk(G) (γ c k (G), respectively). The set D is defined to be a total k-do...

We show that under certain conditions the square of the graph obtained by identifying a vertex in two graphs with hamiltonian square is also hamiltonian. Using this result, we prove necessary and sufficient conditions for hamiltonicity of the square of a connected graph such that every vertex of degree at least three in a block graph corresponds to a cut vertex and any two these vertices are at...

For a finite connected simple graph, the Terwilliger algebra is matrix generated by adjacency and idempotents corresponding to distance partition with respect fixed vertex. We will consider algebras defined two other partitions centralizer of stabilizer vertex in automorphism group graph. give some methods compute such examples for various graphs.

Given a vertex u ∈ V of a graph Γ = (V,E), the (local) proper polynomials constitute a sequence of orthogonal polynomials, constructed from the so-called u-local spectrum of Γ. These polynomials can be thought of as a generalization, for all graphs, of the distance polynomials for the distance-regular graphs. The (local) adjacency polynomials, which are basically sums of proper polynomials, wer...

The vertex-nullity interlace polynomial of a graph, described by Arratia, Bollobás and Sorkin in [ABS00] as evolving from questions of DNA sequencing, and extended to a two-variable interlace polynomial by the same authors in [ABS04b], evokes many open questions. These include relations between the interlace polynomial and the Tutte polynomial and the computational complexity of the vertex-null...

‎Let $G=(V,E)$ be a graph‎. ‎A subset $Ssubset V$ is a hop dominating set‎‎if every vertex outside $S$ is at distance two from a vertex of‎‎$S$‎. ‎A hop dominating set $S$ which induces a connected subgraph‎ ‎is called a connected hop dominating set of $G$‎. ‎The‎‎connected hop domination number of $G$‎, ‎$ gamma_{ch}(G)$,‎‎‎ ‎is the minimum cardinality of a connected hop‎‎dominating set of $G$...

Network science and graph theory are two important branches of mathematics computer science. Many problems in engineering physics modeled with networks graphs. Topological analysis enable researchers to analyse relation some physical properties without conducting expensive experimental studies. indices numerical descriptors which defined by using degree, distance eigen-value notions any graph. ...

Let G be a connected graph with vertex set V and a weight function ρ that assigns a nonnegative number to each of its vertices. Then, the ρ-moment of G at vertex u is defined to be M G(u) = ∑ v∈V ρ(v) dist(u, v), where dist(·, ·) stands for the distance function. Adding up all these numbers, we obtain the ρ-moment of G: M G = ∑ u∈V M G(u) = 1 2 ∑ u,v∈V dist(u, v)[ρ(u) + ρ(v)]. This parameter ge...

We study partially distance-regular graphs and partially walkregular graphs as generalizations of distance-regular graphs and walkregular graphs respectively. We conclude that the partially distanceregular graphs can be viewed as some extremal graphs of partially walk-regular graphs. In the special case that the graph is assumed to be regular with four distinct eigenvalues, a well known class o...