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Over all graphs (or unicyclic graphs) of a given order, we characterise those graphs that minimise or maximise the number of connected induced subgraphs. For each of these classes, we find that the graphs that minimise the number of…

Combinatorics · Mathematics 2019-09-18 Audace A. V. Dossou-Olory

Given a graph on n vertices with m edges, each of unit resistance, how small can the average resistance between pairs of vertices be? There are two very plausible extremal constructions -- graphs like a star, and graphs which are close to…

Combinatorics · Mathematics 2022-06-17 J. Robert Johnson , Mark Walters

We define and study two new kinds of "effective resistances" based on hubs-biased -- hubs-repelling and hubs-attracting -- models of navigating a graph/network. We prove that these effective resistances are squared Euclidean distances…

Spectral Theory · Mathematics 2021-12-03 Ernesto Estrada , Delio Mugnolo

An extremal graph for a given graph $H$ is a graph with maximum number of edges on fixed number of vertices without containing a copy of $H$. The $k$-th power of a path is a graph obtained from a path and joining all pair of vertices of the…

Combinatorics · Mathematics 2020-03-31 Long-Tu Yuan

For a connected graph $G$, its resistance distance matrix is denoted by $R(G)$. A graph is called resistance regular if all the row (or column) sums of $R(G)$ are equal. We provide a necessary and sufficient condition for a simple connected…

Combinatorics · Mathematics 2025-06-13 Haritha T , Chithra A

Let $G=(V(G),E(G))$ be a graph with vertex set $V(G)$ and edge set $E(G)$. The resistance distance $R_G(x,y)$ between two vertices $x,y$ of $G$ is defined to be the effective resistance between the two vertices in the corresponding…

Combinatorics · Mathematics 2024-03-12 Si-Ao Xu , Huan Zhou , Xiang-Feng Pan

We give explicit formulas for resistance distance matrices and Moore-Penrose inverses of incidence and Laplacian matrices of ladder, circular ladder, and M\"{o}bius ladder graphs. As a result, we compute the Kirchhoff index of these graphs…

Combinatorics · Mathematics 2023-06-21 Ali Azimi , Mohammad Farrokhi Derakhshandeh Ghouchan

Let $G$ be a finite, simple connected graph. The average distance of a vertex $v$ of $G$ is the arithmetic mean of the distances from $v$ to all other vertices of $G$. The remoteness $\rho(G)$ of $G$ is the maximum of the average distances…

Combinatorics · Mathematics 2024-05-27 Peter Dankelmann , Sonwabile Mafunda , Sufiyan Mallu

Simplifications of a result from a prior paper concerning the electric resistance between points in a distance-regular graph are given. In particular, we prove that the maximal resistance between points is bounded by twice the resistance…

Combinatorics · Mathematics 2013-03-22 Jacobus Koolen , Greg Markowsky

Let $G$ be a connected graph. The resistance distance between two vertices $u$ and $v$ of $G$, denoted by $R_{G}[u,v]$, is defined as the net effective resistance between them in the electric network constructed from $G$ by replacing each…

Combinatorics · Mathematics 2024-06-21 Wensheng Sun , Yujun Yang , Wuxian Chen , Shou-Jun Xu

Let $G_n$ be a linear crossed polyomino chain with $n$ four-order complete graphs. In this paper, explicit formulas for the Kirchhoff index, the multiplicative degree-Kirchhoff index and the number of spanning trees of $G_n$ are determined,…

Combinatorics · Mathematics 2019-05-17 Yingui Pan , Jianping Li

Given a simple connected graph on $N$ vertices with size $|E|$ and degree sequence $d_{1}\leq d_{2}\leq ...\leq d_{N}$, the aim of this paper is to exhibit new upper and lower bounds for the additive degree-Kirchhoff index in closed forms,…

Combinatorics · Mathematics 2015-03-27 Monica Bianchi , Alessandra Cornaro , José Luis Palacios , Anna Torriero

In this paper, we derive closed-form formulas for resistance distance and Kirchhoff index of graphs with generalized pockets in terms of the resistance distance and Kirchhoff index of the factor graph.

Combinatorics · Mathematics 2019-01-24 Qun Liu

In a connected graph G, the distance between two vertices of G is the length of a shortest path between these vertices. The eccentricity of a vertex u in G is the largest distance between u and any other vertex of G. The total-eccentricity…

Combinatorics · Mathematics 2017-11-21 Rashid Farooq , Mehar Ali Malik , Juan Rada

The Harary index of a graph is defined as the sum of reciprocals of distances between all pairs of vertices of the graph. In this paper we provide an upper bound of the Harary index in terms of the vertex or edge connectivity of a graph. We…

Combinatorics · Mathematics 2014-09-19 Xiao-Xin Li , Yi-Zheng Fan

The vertex $k$-partiteness $v_k(G)$ of graph $G$ is defined as the fewest number of vertices whose deletion from $G$ yields a $k$-partite graph. In this paper, we introduce two concepts: monotonic decreasing topological index and monotonic…

Combinatorics · Mathematics 2017-08-04 Fang Gao , Duo Duo Zhao , Xiao-Xin Li , Jia-Bao Liu

In this paper we give a survey of methods used to calculate values of resistance distance (also known as effective resistance) in graphs. Resistance distance has played a prominent role not only in circuit theory and chemistry, but also in…

Combinatorics · Mathematics 2021-09-15 E. J. Evans , A. E. Francis

The \emph{distance-number} of a graph $G$ is the minimum number of distinct edge-lengths over all straight-line drawings of $G$ in the plane. This definition generalises many well-known concepts in combinatorial geometry. We consider the…

Combinatorics · Mathematics 2008-09-09 Paz Carmi , Vida Dujmović , Pat Morin , David R. Wood

Various topological indices, based on the distances between the vertices of a graph, are widely used in theoretical chemistry. The degree resistance distance of a graph $G$ is defined as ${D_R}(G) = \sum\limits_{\{u,v\} \subseteq V(G)}…

Combinatorics · Mathematics 2016-04-19 Jia-Bao Liu , Xiang-Feng Pan

The distance of a vertex in a graph is the sum of distances from that vertex to all other vertices of the graph. The Wiener index of a graph is the sum of distances between all its unordered pairs of vertices. A graph has been obtained that…

Combinatorics · Mathematics 2024-07-16 Dinesh Pandey