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Let $G$ be a nontrivial connected graph of order $n$ and $k$ an integer with $2\leq k\leq n$. For a set $S$ of $k$ vertices of $G$, let $\kappa (S)$ denote the maximum number $\ell$ of edge-disjoint trees $T_1,T_2,...,T_\ell$ in $G$ such…

Combinatorics · Mathematics 2015-03-17 Shasha Li , Xueliang Li , Yongtang Shi

Let $D=(V,A)$ be a digraph of order $n$, $S$ a subset of $V$ of size $k$ and $2\le k\leq n$. Strong subgraphs $D_1, \dots , D_p$ containing $S$ are said to be internally disjoint if $V(D_i)\cap V(D_j)=S$ and $A(D_i)\cap A(D_j)=\emptyset$…

Discrete Mathematics · Computer Science 2018-03-02 Yuefang Sun , Gregory Gutin

Given a connected graph $G$ and a non-negative integer $g$, the {\em $g$-extra connectivity} $\k_g(G)$ of $G$ is the minimum cardinality of a set of vertices in $G$, if it exists, whose deletion disconnects $G$ and leaves each remaining…

Combinatorics · Mathematics 2018-01-29 Jin-Xin Zhou

The $\ell$-component connectivity (or $\ell$-connectivity for short) of a graph $G$, denoted by $\kappa_\ell(G)$, is the minimum number of vertices whose removal from $G$ results in a disconnected graph with at least $\ell$ components or a…

Discrete Mathematics · Computer Science 2021-05-25 Jou-Ming Chang , Kung-Jui Pai , Ro-Yu Wu , Jinn-Shyong Yang

With graphs considered as natural models for many network design problems, edge connectivity $\kappa'(G)$ and maximum number of edge-disjoint spanning trees $\tau(G)$ of a graph $G$ have been used as measures for reliability and strength in…

Combinatorics · Mathematics 2014-10-22 Xiaofeng Gu , Hong-Jian Lai , Ping Li , Senmei Yao

The generalized $k$-connectivity of a graph $G$, denoted by $\kappa_k(G)$, is a generalization of the traditional connectivity. It is well known that the generalized $k$-connectivity is an important indicator for measuring the fault…

Combinatorics · Mathematics 2021-04-26 Wang Jing , Li Fangmin

The vertex connectivity of a graph $G$ is the size of the smallest set of vertices $S$ such that $G \setminus S$ is disconnected. For the class of planar graphs, the problem of vertex connectivity is well-studied, both from structural and…

Computational Geometry · Computer Science 2025-06-03 Therese Biedl , Karthik Murali

The power graph $\mathcal{P}(G)$ of a given finite group $G$ is the simple undirected graph whose vertices are the elements of $G$, in which two distinct vertices are adjacent if and only if one of them can be obtained as an integral power…

Combinatorics · Mathematics 2018-10-29 Sriparna Chattopadhyay , Kamal Lochan Patra , Binod Kumar Sahoo

Structure connectivity and substructure connectivity are innovative indicators for assessing network reliability and fault tolerance. Similarly, fault diameter evaluates fault tolerance and transmission delays in networks. This paper…

Combinatorics · Mathematics 2025-12-10 Honggang Zhao , Eminjan Sabir , Cheng-Kuan Lin

A cubic graph $G$ is cyclically 5-connected if $G$ is simple, 3-connected, has at least 10 vertices and for every set $F$ of edges of size at most four, at most one component of $G\backslash F$ contains circuits. We prove that if $G$ and…

Combinatorics · Mathematics 2019-05-23 Neil Robertson , P. D. Seymour , Robin Thomas

Let $G$ be a graph of order $n$ and let $u,v$ be vertices of $G$. Let $\kappa_G(u,v)$ denote the maximum number of internally disjoint $u$-$v$ paths in $G$. Then the average connectivity $\overline{\kappa}(G)$ of $G$, is defined as $…

Combinatorics · Mathematics 2021-07-23 Lucas Mol , Ortrud R. Oellermann , Vibhav Oswal

The $g$-extra connectivity is an important parameter to measure the ability of tolerance and reliability of interconnection networks. Given a connected graph $G=(V,E)$ and a non-negative integer $g$, a subset $S\subseteq V$ is called a…

Combinatorics · Mathematics 2020-07-22 He Li , Shumin Zhang , Chengfu Ye

The generalized $k$-connectivity $\kappa_{k}(G)$ of a graph $G$ is a parameter that can measure the reliability of a network $G$ to connect any $k$ vertices in $G$, which is proved to be NP-complete for a general graph $G$. Let $S\subseteq…

Combinatorics · Mathematics 2018-08-31 Shu-Li Zhao , Rong-Xia Hao

A vertex cut $S$ of a connected graph $G$ is a subset of vertices of $G$ whose deletion makes $G$ disconnected. A super vertex cut $S$ of a connected graph $G$ is a subset of vertices of $G$ whose deletion makes $G$ disconnected and there…

Combinatorics · Mathematics 2021-03-19 Yulan Chen , Yuqing Lin , Weigen Yan

Let $D=(V,A)$ be a digraph of order $n$, $S$ a subset of $V$ of size $k$ and $2\le k\leq n$. A strong subgraph $H$ of $D$ is called an $S$-strong subgraph if $S\subseteq V(H)$. A pair of $S$-strong subgraphs $D_1$ and $D_2$ are said to be…

Combinatorics · Mathematics 2022-04-05 Yiling Dong , Gregory Gutin , Yuefang Sun

For a graph $G=(V,E)$ and a set $S\subseteq V(G)$ of size at least $2$, an $S$-Steiner tree $T$ is a subgraph of $G$ that is a tree with $S\subseteq V(T)$. Two $S$-Steiner trees $T$ and $T'$ are internally disjoint (resp. edge-disjoint) if…

Combinatorics · Mathematics 2020-03-10 Shasha Li

The generalized connectivity of a graph, which was introduced recently by Chartrand et al., is a generalization of the concept of vertex connectivity. Let $S$ be a nonempty set of vertices of $G$, a collection $\{T_1,T_2,...,T_r\}$ of trees…

Combinatorics · Mathematics 2011-05-04 Hengzhe Li , Xueliang Li , Yuefang Sun

Let $G$ be a nontrivial connected graph of order $n$, and $k$ an integer with $2\leq k\leq n$. For a set $S$ of $k$ vertices of $G$, let $\kappa (S)$ denote the maximum number $\ell$ of edge-disjoint trees $T_1,T_2,...,T_\ell$ in $G$ such…

Combinatorics · Mathematics 2010-12-30 Shasha Li , Wei Li , Xueliang Li

Let $G$ be a nontrivial connected graph of order $n$ and let $k$ be an integer with $2\leq k\leq n$. For a set $S$ of $k$ vertices of $G$, let $\kappa (S)$ denote the maximum number $\ell$ of edge-disjoint trees $T_1,T_2,...,T_\ell$ in $G$…

Combinatorics · Mathematics 2009-06-18 Shasha Li , Xueliang Li , Wenli Zhou

This paper considers the conditional fault tolerance, $h$-super connectivity $\kappa^{h}$ and $h$-super edge-connectivity $\lambda^{h}$ of the hierarchical cubic network $HCN_n$, an attractive alternative network to the hypercube, and shows…

Combinatorics · Mathematics 2017-09-08 Xiang-Jun Li , Min Liu , Zheng Yan , Jun-Ming Xu