The (revised) Szeged index and the Wiener index of a nonbipartite graph

  • Authors:
  • Lily Chen;Xueliang Li;Mengmeng Liu

  • Affiliations:
  • -;-;-

  • Venue:
  • European Journal of Combinatorics
  • Year:
  • 2014

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Abstract

Hansen et al. used the computer program AutoGraphiX to study the differences between the Szeged index Sz(G) and the Wiener index W(G), and between the revised Szeged index Sz^*(G) and the Wiener index for a connected graph G. They conjectured that for a connected nonbipartite graph G with n=5 vertices and girth g=5, Sz(G)-W(G)=2n-5, and moreover, the bound is best possible when the graph is composed of a cycle C"5 on 5 vertices and a tree T on n-4 vertices sharing a single vertex. They also conjectured that for a connected nonbipartite graph G with n=4 vertices, Sz^*(G)-W(G)=n^2+4n-64, and moreover, the bound is best possible when the graph is composed of a cycle C"3 on 3 vertices and a tree T on n-2 vertices sharing a single vertex. In this paper, we not only give confirmative proofs to these two conjectures but also characterize those graphs that achieve the two lower bounds.