Abstract
The concept of edge connectivity was first proposed by K. Menger, and in communication networks and logical networks, edge connectivity can be used to measure network reliability and fault tolerance. The graph product method can be used to construct complex networks, simulate biological molecule interactions etc. At present, research on the edge connectivity of product graphs mainly focuses on the connectivity of standard product graphs, such as Cartesian product graphs, strong product graphs. The unique properties exhibited by non standard product graphs (such as semi-strong product graphs.) in practical applications are worth further exploration. The concept of semi-strong product was proposed by Mordeson and Chang Shyh, that is, for two graphs and , their semi-strong product is a graph whose vertex set is , and the edge set is defined as follows: if and are two vertices in the semi-strong product , then there is an edge between them if and only if and and are adjacent in , or and are adjacent in and and are adjacent in . And applications of the semi-strong product in fuzzy graphs, symbolic graphs, and finance have shown its broad research prospects. In this article, we mainly study the edge connectivity of semi-strong product graphs, and obtain some exact values. Furthermore, we also give an necessary and sufficient condition for a semi-strong product to be maximally edge-connected.
Keywords
Edge Connectivity, Graph Product, Semi-strong Product
1. Introduction
The concept of edge connectivity was first proposed by K. Menger in 1930s, and a systematic research was obtained by means of Menger's theorem
. Menger's theorem shows that the edge connectivity of a graph is equal to its minimum edge-cut set. This theory lays the foundation for the study of edge connectivity.
With the rapid development of information network, the reliability of network has become one of the key issues in research. Network reliability is usually measured by the connectivity of a graph, such as the edge connectivity is a key parameters to measure network reliability. For example, in communication networks and logical networks, edge connectivity can be used to measure network reliability and fault tolerance
| [2] | Lai, Y. and Hua, X. Component edge connectivity and extra edge connectivity of alternating group networks, J Supercomput. 2024, 80, 313–330.
HYPERLINK " https://doi.org/10.1007/s11227-0" https://doi.org/10.1007/s11227-023-05464-0 |
| [3] | Zhang, G., Yue, Z. and Wang, D. 1-Extra 3-component edge connectivity of modified bubble-sort networks, J Supercomput. 2025, 81, 164.
https://doi.org/10.1007/s11227-024-06610-y |
| [4] | Anastasiia, K., Bonaventura, D. M., Steffen, Z. and Volker, M. Fault Tolerance Placement in the Internet of Things, Proc. ACM Manag. 2024, 138, 1-29.
HYPERLINK " https://doi.org/10.1145/365494" https://doi.org/10.1145/3654941 |
[2-4]
. Edge connectivity is defined as the minimum number of edge deletions required to make a graph disconnected, the concept is particularly important in the design of multiprocessor networks. In addition, edge connectivity is closely related to other properties of graphs, such as diameter, minimum degree, etc. These relationships provide theoretical support for the design and optimization of complex networks.
Product graph is an important construction method in graph theory, which combines the vertices and edges of two or more graphs to generate a new graph. The graph product method can be used to construct complex networks, simulate biological molecule interactions, optimize coding algorithms, and analyze relationships in data visualization
| [5] | Xiang, Y. and Xiang, L. Controllability Gramian-based measures of graph product networks, Sci. China Inf. Sci. 2024, 67, 202207.
HYPERLINK " https://doi.org/10.1007/s11432-023-4034-2" https://doi.org/10.1007/s11432-023-4034-2 |
| [6] | Wang, S., Dong, K. and Liang, D, et al. MIPPIS: protein–protein interaction site prediction network with multi-information fusion, BMC Bioinformatics. 2024, 25, 345.
HYPERLINK " https://doi.org/10.1186/s12859-024-05964-7" https://doi.org/10.1186/s12859-024-05964-7 |
| [7] | Gao, Z., Jiang, C. and Zhang, J, et al. Hierarchical graph learning for protein–protein interaction, Nat Commun. 2023, 14, 1093.
HYPERLINK " https://doi.org/10.1038/s41467-023-36736-1" https://doi.org/10.1038/s41467-023-36736-1 |
[5-7]
. At present, research on the edge connectivity of product graphs mainly focuses on the edge connectivity of standard product graphs, such as Cartesian product graphs, strong product graphs, dictionary product graphs etc.
All graphs in this paper are finite and simple. Let be a simple connected graph, where is the set of vertices of and is the set of edges of . For two graphs and , their Cartesian product is a graph whose vertex set is , and the edge set is defined as follows: if and are two vertices in the Cartesian product , then there is an edge between them if and only if and and are adjacent in , or and are adjacent in and ; their strong product is a graph with whose vertex set is , and the edge set is defined as follows: if and are two vertices in the strong product , then there is an edge between them if and only if and and are adjacent in , or and are adjacent in and , or and are adjacent in and and are adjacent in ; their lexicographic product is a graph with whose vertex set is , and the edge set is defined as follows: if and are two vertices in the lexicographic product , then there is an edge between them if and only if and and are adjacent in , or and are adjacent in .
Let be a simple connected graph. For any vertex of a graph , its vertex-neighbor set is denoted by , which is the set of all vertices adjacent to vertex in the graph . The degree of in the graph is denoted by , which refers to the number of vertices related to in the graph . Therefore, according to the definition of the graph, we have , and the vertices in the graph with degree 0 are called isolated vertices. The minimum degree of the graph is denoted by . If and contains all edges in that satisfy , we say that is a induced subgraph of . Let be a edge subset of , if the induced subgraph of is not connected, then is a edge-cut set of . The edge connectivity of the graph , denoted by , is the cardinality of the minimum edge-cut set of graph . For a connected graph , it is said to be maximally edge-connected if and only if . For two graphs and , we use , , , and to denote the number of vertices, the number of edges, the minimum degree, the edge connectivity and the vertex set of , respectively, where .
For the edge connectivity of Cartesian product, Chiue and Shieh first gave a result in
| [8] | Chiue, W. S. and Shieh, B. S. On connectivity of the Cartesian product of two graphs, Applied Mathematics and Computation. 1999, 102(2-3), 129-137.
HYPERLINK " https://doi.org/10.1016/S0096-3003" https://doi.org/10.1016/S0096-3003(98)10041-3 |
[8]
, that is, for two connected graphs
and
, we have
, and then there has been no good progress. Until Xu and Yang improved the result
in the previous study
, a better result was obtained, that is, for two nontrivial graphs
and
, We have
, and in this article, the author use the edge-version of Menger's theorem to prove the result, then, Klavzar and Spacapan gave a proof in based on the set of minimum edge-cut
| [10] | Klavzar, S. and Spacapan, S. On the edge-connectivity of Cartesian product graphs, Asian-European Journal of Mathematics. 2008, 1(1), 93-98.
HYPERLINK " https://doi.org/10.1142/S1793557108000102" https://doi.org/10.1142/S1793557108000102 |
[10]
. For the edge connectivity of strong product, Researchers proved that for two connected graph
and
, we have
| [11] | Yang, C. and Xu, J. M. Connectivity and edge-connectivity of strong product graphs, J. Univ. Sci. Technol. China. 2008, 38(5), 449-455.
http://staff.ustc.edu.cn/~xujm/200804.pdf |
| [12] | Bresar, B. and Spacapan, S. Edge-connectivity of strong products of graphs, Discus siones Mathematicae Graph Theory. 2007, 27(2): 333-343.
HYPERLINK " https://doi.org/10.7151/dmgt.1365" https://doi.org/10.7151/dmgt.1365 |
[11, 12]
. For the edge connectivity of lexicographic product, Yang and Xu proved that for two graphs
and
, we have
.
The graph product also includes some non-standard products, such as semi strong product etc. The concept of semi-strong product was proposed by Mordeson and Chang Shyh
, and its applications in fuzzy graphs, symbolic graphs, and finance have shown its broad research prospects
| [8] | Chiue, W. S. and Shieh, B. S. On connectivity of the Cartesian product of two graphs, Applied Mathematics and Computation. 1999, 102(2-3), 129-137.
HYPERLINK " https://doi.org/10.1016/S0096-3003" https://doi.org/10.1016/S0096-3003(98)10041-3 |
[8]
.
For two graphs and , their semi-strong product is a graph whose vertex set is , and the edge set is defined as follows: if and are two vertices in the semi-strong product , then there is an edge between them if and only if and and are adjacent in , or and are adjacent in and and are adjacent in .
In this paper, we study the edge connectivity of semi-strong product graphs. Given two graphs and , we obtain that . In further, we also give an necessary and sufficient condition for a semi-strong product to be maximally edge-connected.
2. Preliminaries
For the convenience, we define the following two types of subgraphs. For , we define , it is clear that the subgraph of induced by is isomorphic to . Analogously, for , we define , but it is important to note that the subgraph of induced by is not isomorphic to .
Lemma 2.1 (). For any connected undirected graph
, we have
.
Lemma 2.2. Let and be two graphs, then .
Proof. According to the definition of semi-strong product graph, that is, the semi-strong product of two graphs and is the graph with the vertex set , two vertices and being adjacent in if and only if and is an edge in , or is an edge in and is an edge in , we can get the result of
Assume that
is true, that is
In this case, the product graph will rise to a new edge-connected relation: for two vertices and , they are adjacent in if and only if and is an edge in , or is an edge in and is an edge in , or is an edge in and . At this point, three kinds of connected edges constitute a strong product graph, a contradiction. Therefore,
3. Main Results
Theorem 3.1. Let and be two nontrivial graphs, and is connected, then .
Proof. Let . It is clear that
Let be a minimum cut-set of and there are two connected components and of . Then we can see that in there are exactly edges between and . Hence . Then we have
.(6)
Next we only need to prove that
.(7)
Let be a minimum edge-cut of , and are two connected components of . For , let denote the subgraph of induced by .
It is easy to see that is isomorphic to . Then we define two sets, of which for some and for some .
It is clear that and . If , then it is easy to know that is a partition of . Thus
So we assume that and let .
We need to know that for each neighbor of , the vertex-set of the graph is , and the edge-set between the vertex-sets and is , denoted by , has edge-connectivity .
Let , then for each neighbor of ; otherwise is connected through , which contradicts to our hypothesis.
In the following, we claim that , of which and is a neighbor of . Then let , , and we assume that .
Case 1: .
If , then holds, since .
Case 2: .
If , we can find edge-disjoint -paths in . Let and . Then for each , there are edge-disjoint -paths in : with . So we can find edge-disjoint -paths.
For the sake of disconnected from , we must have and also holds.
Let be neighbors of in , then
.(9)
This completes the proof.
Corollary 3.1. Let and be two connected graphs, then is maximally edge connected if and only if .
4. Conclusions
The main conclusion of this paper is as follows: for two nontrivial graphs and , and is connected, then we have . Furthermore, we obtain an necessary and sufficient condition for a semi-strong product to be maximally edge-connected.
At present, research on the edge connectivity of product graphs mainly focuses on the edge connectivity of standard product graphs, such as Cartesian product graphs, strong product graphs, lexicographic product graphs etc. The graph product also includes some non-standard products, such as semi-strong products, etc. The unique properties exhibited by non-standard product graphs (such as semi-strong product graphs, etc.) in practical applications are worth further exploration.
Author Contributions
Qiaoling Wang: Conceptualization, Resources, Software, Formal Analysis, Validation, Investigation, Visualization, Methodology, Writing – original draft
Haizhen Ren: Data curation, Supervision, Funding acquisition, Project administration, Writing – review & editing
Funding
This work was partially supported by the National Natural Science Foundation of China (Grant Nos. 12161073).
Data Availability Statement
The data supporting the outcome of this research work has been reported in this manuscript.
Conflicts of Interest
The authors declare no conflicts of interest.
References
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Cite This Article
-
-
@article{10.11648/j.acm.20251406.15,
author = {Qiaoling Wang and Haizhen Ren},
title = {On the Edge Connectivity of Semi-strong Product Graphs},
journal = {Applied and Computational Mathematics},
volume = {14},
number = {6},
pages = {356-359},
doi = {10.11648/j.acm.20251406.15},
url = {https://doi.org/10.11648/j.acm.20251406.15},
eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.acm.20251406.15},
abstract = {The concept of edge connectivity was first proposed by K. Menger, and in communication networks and logical networks, edge connectivity can be used to measure network reliability and fault tolerance. The graph product method can be used to construct complex networks, simulate biological molecule interactions etc. At present, research on the edge connectivity of product graphs mainly focuses on the connectivity of standard product graphs, such as Cartesian product graphs, strong product graphs. The unique properties exhibited by non standard product graphs (such as semi-strong product graphs.) in practical applications are worth further exploration. The concept of semi-strong product was proposed by Mordeson and Chang Shyh, that is, for two graphs and , their semi-strong product is a graph whose vertex set is , and the edge set is defined as follows: if and are two vertices in the semi-strong product , then there is an edge between them if and only if and and are adjacent in , or and are adjacent in and and are adjacent in . And applications of the semi-strong product in fuzzy graphs, symbolic graphs, and finance have shown its broad research prospects. In this article, we mainly study the edge connectivity of semi-strong product graphs, and obtain some exact values. Furthermore, we also give an necessary and sufficient condition for a semi-strong product to be maximally edge-connected.},
year = {2025}
}
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TY - JOUR
T1 - On the Edge Connectivity of Semi-strong Product Graphs
AU - Qiaoling Wang
AU - Haizhen Ren
Y1 - 2025/12/11
PY - 2025
N1 - https://doi.org/10.11648/j.acm.20251406.15
DO - 10.11648/j.acm.20251406.15
T2 - Applied and Computational Mathematics
JF - Applied and Computational Mathematics
JO - Applied and Computational Mathematics
SP - 356
EP - 359
PB - Science Publishing Group
SN - 2328-5613
UR - https://doi.org/10.11648/j.acm.20251406.15
AB - The concept of edge connectivity was first proposed by K. Menger, and in communication networks and logical networks, edge connectivity can be used to measure network reliability and fault tolerance. The graph product method can be used to construct complex networks, simulate biological molecule interactions etc. At present, research on the edge connectivity of product graphs mainly focuses on the connectivity of standard product graphs, such as Cartesian product graphs, strong product graphs. The unique properties exhibited by non standard product graphs (such as semi-strong product graphs.) in practical applications are worth further exploration. The concept of semi-strong product was proposed by Mordeson and Chang Shyh, that is, for two graphs and , their semi-strong product is a graph whose vertex set is , and the edge set is defined as follows: if and are two vertices in the semi-strong product , then there is an edge between them if and only if and and are adjacent in , or and are adjacent in and and are adjacent in . And applications of the semi-strong product in fuzzy graphs, symbolic graphs, and finance have shown its broad research prospects. In this article, we mainly study the edge connectivity of semi-strong product graphs, and obtain some exact values. Furthermore, we also give an necessary and sufficient condition for a semi-strong product to be maximally edge-connected.
VL - 14
IS - 6
ER -
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