Identical Neighbor Structure: Effects on Spectrum and Independence in <i>CN</i><sub>s</sub> Cartesian Product of Graphs

In this study, we introduced a novel graph product derived from the standard Cartesian product and investigated its structural properties, with a particular emphasis on its independence number and spectral characteristics in relation to identical neighbor structures. A key finding is that the spectr...

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Main Authors: Subha A B, Sreekumar K G, Elsayed M. Elsayed, Manilal K, Turki D. Alharbi
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Mathematics
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Online Access:https://www.mdpi.com/2227-7390/13/7/1040
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author Subha A B
Sreekumar K G
Elsayed M. Elsayed
Manilal K
Turki D. Alharbi
author_facet Subha A B
Sreekumar K G
Elsayed M. Elsayed
Manilal K
Turki D. Alharbi
author_sort Subha A B
collection DOAJ
description In this study, we introduced a novel graph product derived from the standard Cartesian product and investigated its structural properties, with a particular emphasis on its independence number and spectral characteristics in relation to identical neighbor structures. A key finding is that the spectrum of this newly defined product graph consists entirely of integral eigenvalues, a significant property with applications in chemistry, network theory, and combinatorial optimization. We defined <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> vertices as the vertices having an identical set of neighbors and classified graphs containing such vertices as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> graphs. Furthermore, we introduced the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> Cartesian product for these graphs. To formally characterize the relationships between <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> vertices, we constructed an <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>n</mi><mo>×</mo><mi>n</mi></mrow></semantics></math></inline-formula><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> matrix, where an entry is 1 if the corresponding pair of vertices are <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> vertices and 0 otherwise. Utilizing this matrix, we established that the spectrum of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> Cartesian product consists exclusively of integral eigenvalues. This finding enhances our understanding of graph spectra and their relation to structural properties.
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spelling doaj-art-4082ca5bacd443409743e547fd7db1752025-08-20T02:17:00ZengMDPI AGMathematics2227-73902025-03-01137104010.3390/math13071040Identical Neighbor Structure: Effects on Spectrum and Independence in <i>CN</i><sub>s</sub> Cartesian Product of GraphsSubha A B0Sreekumar K G1Elsayed M. Elsayed2Manilal K3Turki D. Alharbi4Department of Mathematics, University College, University of Kerala, Thiruvananthapuram 695034, IndiaDepartment of Mathematics, University of Kerala, Thiruvananthapuram 695581, IndiaDepartment of Mathematics, Faculty of Science, King AbdulAziz University, Jeddah 21589, Saudi ArabiaDepartment of Mathematics, University College, University of Kerala, Thiruvananthapuram 695034, IndiaDepartment of Mathematics, Al-Leith University College, Umm Al-Qura University, Mecca 24382, Saudi ArabiaIn this study, we introduced a novel graph product derived from the standard Cartesian product and investigated its structural properties, with a particular emphasis on its independence number and spectral characteristics in relation to identical neighbor structures. A key finding is that the spectrum of this newly defined product graph consists entirely of integral eigenvalues, a significant property with applications in chemistry, network theory, and combinatorial optimization. We defined <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> vertices as the vertices having an identical set of neighbors and classified graphs containing such vertices as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> graphs. Furthermore, we introduced the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> Cartesian product for these graphs. To formally characterize the relationships between <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> vertices, we constructed an <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>n</mi><mo>×</mo><mi>n</mi></mrow></semantics></math></inline-formula><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> matrix, where an entry is 1 if the corresponding pair of vertices are <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> vertices and 0 otherwise. Utilizing this matrix, we established that the spectrum of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>C</mi><msub><mi>N</mi><mi>s</mi></msub></mrow></semantics></math></inline-formula> Cartesian product consists exclusively of integral eigenvalues. This finding enhances our understanding of graph spectra and their relation to structural properties.https://www.mdpi.com/2227-7390/13/7/1040<i>CN<sub>S</sub></i> graph<i>DN<sub>S</sub></i> graph<i>CN<sub>S</sub></i> matrixindependence number<i>CN<sub>S</sub></i> spectrum<i>CN<sub>S</sub></i> energy
spellingShingle Subha A B
Sreekumar K G
Elsayed M. Elsayed
Manilal K
Turki D. Alharbi
Identical Neighbor Structure: Effects on Spectrum and Independence in <i>CN</i><sub>s</sub> Cartesian Product of Graphs
Mathematics
<i>CN<sub>S</sub></i> graph
<i>DN<sub>S</sub></i> graph
<i>CN<sub>S</sub></i> matrix
independence number
<i>CN<sub>S</sub></i> spectrum
<i>CN<sub>S</sub></i> energy
title Identical Neighbor Structure: Effects on Spectrum and Independence in <i>CN</i><sub>s</sub> Cartesian Product of Graphs
title_full Identical Neighbor Structure: Effects on Spectrum and Independence in <i>CN</i><sub>s</sub> Cartesian Product of Graphs
title_fullStr Identical Neighbor Structure: Effects on Spectrum and Independence in <i>CN</i><sub>s</sub> Cartesian Product of Graphs
title_full_unstemmed Identical Neighbor Structure: Effects on Spectrum and Independence in <i>CN</i><sub>s</sub> Cartesian Product of Graphs
title_short Identical Neighbor Structure: Effects on Spectrum and Independence in <i>CN</i><sub>s</sub> Cartesian Product of Graphs
title_sort identical neighbor structure effects on spectrum and independence in i cn i sub s sub cartesian product of graphs
topic <i>CN<sub>S</sub></i> graph
<i>DN<sub>S</sub></i> graph
<i>CN<sub>S</sub></i> matrix
independence number
<i>CN<sub>S</sub></i> spectrum
<i>CN<sub>S</sub></i> energy
url https://www.mdpi.com/2227-7390/13/7/1040
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AT sreekumarkg identicalneighborstructureeffectsonspectrumandindependenceinicnisubssubcartesianproductofgraphs
AT elsayedmelsayed identicalneighborstructureeffectsonspectrumandindependenceinicnisubssubcartesianproductofgraphs
AT manilalk identicalneighborstructureeffectsonspectrumandindependenceinicnisubssubcartesianproductofgraphs
AT turkidalharbi identicalneighborstructureeffectsonspectrumandindependenceinicnisubssubcartesianproductofgraphs