scholarly journals On the Harary index of cacti

Filomat ◽  
2014 ◽  
Vol 28 (3) ◽  
pp. 493-507 ◽  
Author(s):  
Zhongxun Zhu ◽  
Ting Tao ◽  
Jing Yu ◽  
Liansheng Tan
Keyword(s):  
Connected Graph ◽  
Perfect Matching ◽  
Upper Bounds ◽  
Common Vertex ◽  
Harary Index

The Harary index is defined as the sum of reciprocals of distances between all pairs of vertices of a connected graph. A connected graph G is a cactus if any two of its cycles have at most one common vertex. Let G(n, r) be the set of cacti of order n and with r cycles, ?(2n,r) the set of cacti of order 2n with a perfect matching and r cycles. In this paper, we give the sharp upper bounds of the Harary index of cacti among G (n,r) and ?(2n, r), respectively, and characterize the corresponding extremal cactus.

scholarly journals Reciprocal product-degree distance of graphs

Filomat ◽  
2016 ◽  
Vol 30 (8) ◽  
pp. 2217-2231
Author(s):  
Guifu Su ◽  
Liming Xiong ◽  
Ivan Gutman ◽  
Lan Xu
Keyword(s):  
Connected Graph ◽  
Upper Bounds ◽  
Graph Invariant ◽  
Lower And Upper Bounds ◽  
Harary Index ◽  
Underlying Graph ◽  
Degree Distance ◽  
Degree Modification ◽  
Type Relation

We investigate a new graph invariant named reciprocal product-degree distance, defined as: RDD* = ?{u,v}?V(G)u?v deg(u)?deg(v)/dist(u,v) where deg(v) is the degree of the vertex v, and dist(u,v) is the distance between the vertices u and v in the underlying graph. RDD* is a product-degree modification of the Harary index. We determine the connected graph of given order with maximum RDD*-value, and establish lower and upper bounds for RDD*. Also a Nordhaus-Gaddum-type relation for RDD* is obtained.

scholarly journals Upper bounds on the energy of graphs in terms of matching number

2021 ◽  
pp. 16-16
Author(s):  
Saieed Akbari ◽  
Abdullah Alazemi ◽  
Milica Andjelic
Keyword(s):  
Adjacency Matrix ◽  
Connected Graph ◽  
Short Proof ◽  
Upper Bounds ◽  
Vertex Degree ◽  
Maximum Matching ◽  
Matching Number ◽  
Open Problems

The energy of a graph G, ?(G), is the sum of absolute values of the eigenvalues of its adjacency matrix. The matching number ?(G) is the number of edges in a maximum matching. In this paper, for a connected graph G of order n with largest vertex degree ? ? 6 we present two new upper bounds for the energy of a graph: ?(G) ? (n-1)?? and ?(G) ? 2?(G)??. The latter one improves recently obtained bound ?(G) ? {2?(G)?2?e + 1, if ?e is even; ?(G)(? a + 2?a + ?a-2?a), otherwise, where ?e stands for the largest edge degree and a = 2(?e + 1). We also present a short proof of this result and several open problems.

A Note on Primitive Graphs

1972 ◽  
Vol 15 (3) ◽  
pp. 437-440 ◽  
Author(s):  
I. Z. Bouwer ◽  
G. F. LeBlanc
Keyword(s):  
Connected Graph ◽  
Common Vertex ◽  
Connected Subgraph ◽  
Property A ◽  
Vertex Set

Let G denote a connected graph with vertex set V(G) and edge set E(G). A subset C of E(G) is called a cutset of G if the graph with vertex set V(G) and edge set E(G)—C is not connected, and C is minimal with respect to this property. A cutset C of G is simple if no two edges of C have a common vertex. The graph G is called primitive if G has no simple cutset but every proper connected subgraph of G with at least one edge has a simple cutset. For any edge e of G, let G—e denote the graph with vertex set V(G) and with edge set E(G)—e.

scholarly journals Proper Vertex Connection and Graph Operations

2019 ◽  
Vol 19 (02) ◽  
pp. 1950001
Author(s):  
YINGYING ZHANG ◽  
XIAOYU ZHU
Keyword(s):  
Direct Product ◽  
Connected Graph ◽  
Upper Bounds ◽  
Lexicographic Product ◽  
Colored Graph ◽  
Connection Number ◽  
Graph Operations ◽  
Proper Vertex

A path in a vertex-colored graph is a vertex-proper path if any two internal adjacent vertices differ in color. A vertex-colored graph is proper vertex k-connected if any two vertices of the graph are connected by k disjoint vertex-proper paths of the graph. For a k-connected graph G, the proper vertex k-connection number of G, denoted by pvck(G), is defined as the smallest number of colors required to make G proper vertex k-connected. A vertex-colored graph is strong proper vertex-connected, if for any two vertices u, v of the graph, there exists a vertex-proper u-v geodesic. For a connected graph G, the strong proper vertex-connection number of G, denoted by spvc(G), is the smallest number of colors required to make G strong proper vertex-connected. In this paper, we study the proper vertex k-connection number and the strong proper vertex-connection number on the join of two graphs, the Cartesian, lexicographic, strong and direct product, and present exact values or upper bounds for these operations of graphs. Then we apply these results to some instances of Cartesian and lexicographic product networks.

scholarly journals Some Bounds for the Kirchhoff Index of Graphs

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Yujun Yang
Keyword(s):  
Connected Graph ◽  
Planar Graphs ◽  
Independence Number ◽  
Clique Number ◽  
Upper Bounds ◽  
Electrical Network ◽  
Lower And Upper Bounds ◽  
Kirchhoff Index ◽  
Resistance Distance ◽  
Fullerene Graphs

The resistance distance between two vertices of a connected graphGis defined as the effective resistance between them in the corresponding electrical network constructed fromGby replacing each edge ofGwith a unit resistor. The Kirchhoff index ofGis the sum of resistance distances between all pairs of vertices. In this paper, general bounds for the Kirchhoff index are given via the independence number and the clique number, respectively. Moreover, lower and upper bounds for the Kirchhoff index of planar graphs and fullerene graphs are investigated.

scholarly journals Harary index of the k-th power of a graph

2013 ◽  
Vol 7 (1) ◽  
pp. 94-105 ◽  
Author(s):  
Guifu Su ◽  
Liming Xiong ◽  
Ivan Gutman
Keyword(s):  
Type Inequality ◽  
Upper Bounds ◽  
Lower And Upper Bounds ◽  
Harary Index ◽  
Underlying Graph

The k-th power of a graph G, denoted by Gk, is a graph with the same set of vertices as G, such that two vertices are adjacent in Gk if and only if their distance in G is at most k. The Harary index H is the sum of the reciprocal distances of all pairs of vertices of the underlying graph. Lower and upper bounds on H(Gk) are obtained. A Nordhaus-Gaddum type inequality for H(Gk) is also established.

scholarly journals On the reformulated reciprocal degree distance of graphs

2016 ◽  
Vol 25 (2) ◽  
pp. 205-213
Author(s):  
K. PATTABIRAMAN ◽  
◽  
M. VIJAYARAGAVAN ◽  
Keyword(s):  
Connected Graph ◽  
Cartesian Product ◽  
Vertex Degree ◽  
Symmetric Difference ◽  
Weighted Sum ◽  
Graph Invariant ◽  
Harary Index ◽  
Degree Distance

The reciprocal degree distance (RDD), defined for a connected graph G as vertex-degree-weighted sum of the reciprocal distances, that is, RDD(G) = P u,v∈V (G) (d(u)+d(v)) dG(u,v) . The new graph invariant named reformulated reciprocal degree distance is defined for a connected graph G as Rt(G) = P u,v∈V (G) (d(u)+d(v)) dG(u,v)+t , t ≥ 0. The reformulated reciprocal degree distance is a weight version of the t-Harary index, that is, Ht(G) = P u,v∈V (G) 1 dG(u,v)+t , t ≥ 0. In this paper, the reformulated reciprocal degree distance and reciprocal degree distance of disjunction, symmetric difference, Cartesian product of two graphs are obtained. Finally, we obtain the reformulated reciprocal degree distance and reciprocal degree distance of double a graph.

scholarly journals Edge Mostar Indices of Cacti Graph With Fixed Cycles

2021 ◽  
Vol 9 ◽  
Author(s):  
Farhana Yasmeen ◽  
Shehnaz Akhter ◽  
Kashif Ali ◽  
Syed Tahir Raza Rizvi
Keyword(s):  
Upper Bound ◽  
Connected Graph ◽  
Thermodynamic Characteristics ◽  
Chemical Compounds ◽  
Fixed Number ◽  
Common Vertex ◽  
Topological Invariants ◽  
Cactus Graph ◽  
Number Of Cycles

Topological invariants are the significant invariants that are used to study the physicochemical and thermodynamic characteristics of chemical compounds. Recently, a new bond additive invariant named the Mostar invariant has been introduced. For any connected graph ℋ, the edge Mostar invariant is described as Moe(ℋ)=∑gx∈E(ℋ)|mℋ(g)−mℋ(x)|, where mℋ(g)(or mℋ(x)) is the number of edges of ℋ lying closer to vertex g (or x) than to vertex x (or g). A graph having at most one common vertex between any two cycles is called a cactus graph. In this study, we compute the greatest edge Mostar invariant for cacti graphs with a fixed number of cycles and n vertices. Moreover, we calculate the sharp upper bound of the edge Mostar invariant for cacti graphs in ℭ(n,s), where s is the number of cycles.

scholarly journals DIMENSI PARTISI GRAF THORN DARI GRAF RODA W3 DAN W4

2019 ◽  
Vol 16 (1) ◽  
pp. 110-115
Author(s):  
R Riza ◽  
S Zayendra ◽  
A Mardhaningsih
Keyword(s):  
Connected Graph ◽  
Upper Bounds ◽  
Wheel Graph ◽  
Partition Dimension ◽  
Thorn Graph

Let 𝐺 = (𝑉, 𝐸) be a connected graph and 𝑆 ⊆ 𝑉(𝐺). For a vertex v ∈ V(G) and an ordered k-partition Π = {𝑆1 , 𝑆2 , … , 𝑆𝑘 } of 𝑉(𝐺), the representation of v with respect to Π is the k-vector 𝑟(𝑣|𝛱 = (𝑑(𝑣, 𝑆1), 𝑑(𝑣, 𝑆2), . . . , 𝑑(𝑣, 𝑆𝑘)), where d(v,Si) denotes the distance between v and Si. The k-partition Π is said to be resolving if for every two vertices 𝑢, 𝑣  𝑉(𝐺), the representation 𝑟(𝑢|П)  𝑟(𝑣|Π). The minimum k for which there is a resolving k-partition of 𝑉(𝐺) is called the partition dimension of 𝐺, denoted by 𝑝𝑑(𝐺). The wheel graph 𝑊𝑛 𝑜𝑛 𝑛 + 1 vertices with 𝑉(𝑊𝑛) = {𝑣0, 𝑣1, . . . , 𝑣𝑛}. Let 𝑙2 ,𝑙2 ,… ,𝑙𝑛be non-negative integers, 𝑙𝑖 ≥ 1, for 𝑖  {0,1,2, . . . , 𝑛}. The thorn graph of the graph Wn, with parameters 𝑙0 ,𝑙1 ,… ,𝑙𝑛 is obtained by attaching li new vertices of degree one to the vertex vi of the graph Wn. The thorn graph is denoted by 𝑇ℎ(𝑊𝑛,𝑙0 ,𝑙1 ,… ,𝑙𝑛). In this paper we give the upper bounds for the partition dimension of 𝑊3 and 𝑊4 denoted by 𝑝𝑑(𝑇ℎ(𝑊3 ,𝑙0 ,𝑙1 ,𝑙2 ,𝑙3 )) and 𝑝𝑑(𝑇ℎ(𝑊4 ,𝑙0 ,𝑙1 ,𝑙2 ,𝑙3 ,𝑙4 )). Keywords : Partition Dimension, Resolving Partition, Thorn Graph, Wheel Graph.

scholarly journals Upper Bounds for the Modified Second Multiplicative Zagreb Index of Graph Operations

2016 ◽  
Vol 17 ◽  
pp. 10-16
Author(s):  
Bommanahal Basavanagoud ◽  
Shreekant Patil
Keyword(s):  
Connected Graph ◽  
Cartesian Product ◽  
Upper Bounds ◽  
Zagreb Index ◽  
Graph Operations ◽  
Product Composition ◽  
Degree Of A Vertex ◽  
Product Of Graphs ◽  
Corona Product

The modified second multiplicative Zagreb index of a connected graph G, denoted by $\prod_{2}^{*}(G)$, is defined as $\prod_{2}^{*}(G)=\prod \limits_{uv\in E(G)}[d_{G}(u)+d_{G}(v)]^{[d_{G}(u)+d_{G}(v)]}$ where $d_{G}(z)$ is the degree of a vertex z in G. In this paper, we present some upper bounds for the modified second multiplicative Zagreb index of graph operations such as union, join, Cartesian product, composition and corona product of graphs are derived.The modified second multiplicative Zagreb index of aconnected graph , denoted by , is defined as where is the degree of avertex in . In this paper, we present some upper bounds for themodified second multiplicative Zagreb index of graph operations such as union,join, Cartesian product, composition and corona product of graphs are derived.

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