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https://www.um.edu.mt/library/oar/handle/123456789/65153
Title: | On the displacement of eigenvalues when removing a twin vertex |
Authors: | Briffa, Johann A. Sciriha, Irene |
Keywords: | Graph theory Mathematics Eigenvalues Threshold logic |
Issue Date: | 2020 |
Publisher: | Technical University Zielona Gora. Institute of Mathematics |
Citation: | Briffa, J. A., & Sciriha, I. (2020). On the displacement of eigenvalues when removing a twin vertex. Discussiones Mathematicae Graph Theory, 40(2), 435-450. |
Abstract: | Twin vertices of a graph have the same open neighbourhood. If they are not adjacent, then they are called duplicates and contribute the eigenvalue zero to the adjacency matrix. Otherwise they are termed co-duplicates, when they contribute −1 as an eigenvalue of the adjacency matrix. On removing a twin vertex from a graph, the spectrum of the adjacency matrix does not only lose the eigenvalue 0 or −1. The perturbation sends a rippling effect to the spectrum. The simple eigenvalues are displaced. We obtain a closed formula for the characteristic polynomial of a graph with twin vertices in terms of two polynomials associated with the perturbed graph. These are used to obtain estimates of the displacements in the spectrum caused by the perturbation. |
URI: | https://www.um.edu.mt/library/oar/handle/123456789/65153 |
Appears in Collections: | Scholarly Works - FacSciMat |
Files in This Item:
File | Description | Size | Format | |
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DMGT-2274Dups.pdf | 540.07 kB | Adobe PDF | View/Open |
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