SOFT COMPUTING, vol.1, no.1, pp.1-13, 2023 (SCI-Expanded)
The vulnerability analysis of networks is a central goal within the concept of graph-theoretic problems. Therefore, graph
theory serves as an essential scientific tool for studying the reliability and robustness of networks. Vertex centrality has great
importance in the context of network analysis. One of the metrics used in network analysis is closeness centrality, which is
a structural measure that evaluates the importance of a node in a network. This measure is based on the sum of the distances
between the node and all other nodes in the network. This paper analyzes the closeness of different tree structures. In addition,
formulas for the closeness of k-ary trees, binomial trees, comet graphs, double comet graphs, double star graphs, and Et
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graphs are established. Upper and lower bounds are studied for k-ary and binary trees. Upper bounds arise from the perfect
form of the tree for the k-ary tree and its special structure of the binary tree. Moreover, some numerical experiments are
conducted on the considered graph structures. The results are supported the robustness of the double star graph structure in
terms of closeness centrality. Furthermore, we present a relevant application problem within the context of this study.