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Title: | Repeated eigenvalues of the line graph of a tree and of its deck |
Authors: | Sciriha, Irene |
Keywords: | Eigenvalues -- Problems, exercises, etc. Polynomials -- Mathematical models Mathematics -- Charts, diagrams, etc. Mathematics -- Graphic methods |
Issue Date: | 2006 |
Publisher: | University of Manitoba. Department of Computer Science |
Citation: | Sciriha, I. (2006). Repeated eigenvalues of the line graph of a tree and of its deck. Utilitas Mathematica, 71, 33-55. |
Abstract: | For a graph G on vertices v1, v2,..., vn, the p-deck of G consists of n cards each showing the characteristic polynomial φ(G-vi) of the adjacency matrix of a vertex-deleted subgraph G-vi, i = 1,2,..., n. Equivalently, a card shows the roots of G-vi, which are the eigenvalues of the adjacency matrix of G - v i. We determine certain structural features of a line graph L T of a tree T that indicate the repetition of particular eigenvalues on at least one card of the p-deck. The occurrence of repeated eigenvalues enables a constructive solution to the polynomial reconstruction problem. It is shown that the p-deck of the line graph of a tree LT, LT ≠ K3, with at least one terminal clique Kr, r > 2, contains a card with repeated eigenvalues. For exactly one terminal clique, K3, with the rest being K2s, (-1) or the pair ±√5-1/2 are the repeated eigenvalues that appear in the p-deck. The remaining line graphs of trees have only K2s as terminal cliques. The singular ones among these have a card with the eigenvalue zero repeated. |
URI: | https://utilitasmathematica.com/index.php/Index/article/view/413 https://www.um.edu.mt/library/oar/handle/123456789/108053 |
Appears in Collections: | Scholarly Works - FacSciMat |
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Repeated eigenvalues of the line graph of a tree and of its deck 2006.pdf Restricted Access | 529.62 kB | Adobe PDF | View/Open Request a copy |
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