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Wyszukujesz frazę "Eigenvalues" wg kryterium: Temat


Wyświetlanie 1-11 z 11
Tytuł:
Some additions to the theory of star partitions of graphs
Autorzy:
Bell, Francis
Cvetković, Dragos
Rowlinson, Peter
Simić, Slobodan
Powiązania:
https://bibliotekanauki.pl/articles/744251.pdf
Data publikacji:
1999
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graph
eigenvalues
eigenspaces
star partitions
Opis:
This paper contains a number of results in the theory of star partitions of graphs. We illustrate a variety of situations which can arise when the Reconstruction Theorem for graphs is used, considering in particular galaxy graphs - these are graphs in which every star set is independent. We discuss a recursive ordering of graphs based on the Reconstruction Theorem, and point out the significance of galaxy graphs in this connection.
Źródło:
Discussiones Mathematicae Graph Theory; 1999, 19, 2; 119-134
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determining Graphs by the Complementary Spectrum
Autorzy:
Pinheiro, Lucélia K.
Souza, Bruna S.
Trevisan, Vilmar
Powiązania:
https://bibliotekanauki.pl/articles/31562123.pdf
Data publikacji:
2020-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
graphs
complementary eigenvalues
graph isomorphism
Opis:
The complementary spectrum of a connected graph G is the set of the complementary eigenvalues of the adjacency matrix of G. In this note, we discuss the possibility of representing G using this spectrum. On one hand, we give evidence that this spectrum distinguishes more graphs than other standard graph spectra. On the other hand, we show that it is hard to compute the complementary spectrum. In particular, we see that computing the complementary spectrum is equivalent to finding all connected induced subgraphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 2; 607-620
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A result related to the largest eigenvalue of a tree
Autorzy:
Vijayakumar, Gurusamy
Powiązania:
https://bibliotekanauki.pl/articles/743093.pdf
Data publikacji:
2008
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
eigenvalues of a graph
characteristic polynomial
Opis:
In this note we prove that {0,1,√2,√3,2} is the set of all real numbers l such that the following holds: every tree having an eigenvalue which is larger than l has a subtree whose largest eigenvalue is l.
Źródło:
Discussiones Mathematicae Graph Theory; 2008, 28, 3; 557-561
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spectral integral variation of trees
Autorzy:
Wang, Yi
Fan, Yi-Zheng
Powiązania:
https://bibliotekanauki.pl/articles/743873.pdf
Data publikacji:
2006
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
tree
Laplacian eigenvalues
spectral integral variation
algebraic connectivity
Opis:
In this paper, we determine all trees with the property that adding a particular edge will result in exactly two Laplacian eigenvalues increasing respectively by 1 and the other Laplacian eigenvalues remaining fixed. We also investigate a situation in which the algebraic connectivity is one of the changed eigenvalues.
Źródło:
Discussiones Mathematicae Graph Theory; 2006, 26, 1; 49-58
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Balancedness and the Least Laplacian Eigenvalue of Some Complex Unit Gain Graphs
Autorzy:
Belardo, Francesco
Brunetti, Maurizio
Reff, Nathan
Powiązania:
https://bibliotekanauki.pl/articles/31540652.pdf
Data publikacji:
2020-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
gain graph
Laplacian eigenvalues
balanced graph
algebraic frustration
Opis:
Let \(\mathbb{T}_4 = {±1, ±i}\) be the subgroup of 4-th roots of unity inside \(\mathbb{T}\), the multiplicative group of complex units. A complex unit gain graph \(\Phi\) is a simple graph $Γ = (V(Γ) = {v_1, . . ., v_n}, E(Γ))$ equipped with a map \(\varphi:\overrightarrow{E}(Γ)→\mathbb{T}\) defined on the set of oriented edges such that \(\varphi(v_iv_j) = \varphi(v_jv_i)^{−1}\). The gain graph \(\Phi\) is said to be balanced if for every cycle $C = v_{i_1}v_{i_2} . . . v_{i_k}v_{i_1}$ we have \(\varphi(v_{i_1}v_{i_2})\varphi(v_{i_2}v_{i_3}) . . . \varphi(v_{i_k}v_{i_1}) = 1\). It is known that \(\Phi\) is balanced if and only if the least Laplacian eigenvalue \(\lambda_n(\Phi)\) is 0. Here we show that, if \(\Phi\) is unbalanced and \(\varphi(\Phi) ⊆ \mathbb{T}_4\), the eigenvalue \(\lambda_n(\Phi)\) measures how far is \(\Phi\) from being balanced. More precisely, let \(ν(\Phi)\) (respectively, \(∈(\Phi)\)) be the number of vertices (respectively, edges) to cancel in order to get a balanced gain subgraph. We show that \(\lambda_n(\Phi) ≤ ν(\Phi) ≤ ∈(\Phi)\). We also analyze the case when \(\lambda_n(\Phi) = ν(\Phi)\). In fact, we identify the structural conditions on \(\Phi\) that lead to such equality.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 2; 417-433
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On melancholic magic squares
Autorzy:
Trenkler, Götz
Trenkler, Dietrich
Powiązania:
https://bibliotekanauki.pl/articles/729848.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
magic squares
patterns
group inverse
Moore-Penrose inverse
eigenvalues and eigenvectors
Opis:
Starting with Dürer's magic square which appears in the well-known copper plate engraving Melencolia we consider the class of melancholic magic squares. Each member of this class exhibits the same 86 patterns of Dürer's magic square and is magic again. Special attention is paid to the eigenstructure of melancholic magic squares, their group inverse and their Moore-Penrose inverse. It is seen how the patterns of the original Dürer square to a large extent are passed down also to the inverses of the melancholic magic squares.
Źródło:
Discussiones Mathematicae Probability and Statistics; 2013, 33, 1-2; 111-119
1509-9423
Pojawia się w:
Discussiones Mathematicae Probability and Statistics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Number of P-Vertices of Singular Acyclic Matrices: An Inverse Problem
Autorzy:
Du, Zhibin
da Fonseca, Carlos M.
Powiązania:
https://bibliotekanauki.pl/articles/31804164.pdf
Data publikacji:
2020-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
trees
acyclic matrices
singular
multiplicity of eigenvalues
P-set
P-vertices
Opis:
Let A be a real symmetric matrix. If after we delete a row and a column of the same index, the nullity increases by one, we call that index a P-vertex of A. When A is an n × n singular acyclic matrix, it is known that the maximum number of P-vertices is n − 2. If T is the underlying tree of A, we will show that for any integer number k ∈ {0, 1, . . ., n − 2}, there is a (singular) matrix whose graph is T and with k P-vertices. We will provide illustrative examples.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 2; 525-532
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On composition of signed graphs
Autorzy:
Shahul Hameed, K.
Germina, K.
Powiązania:
https://bibliotekanauki.pl/articles/743222.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
signed graph
eigenvalues
graph composition
regular graphs
net-regular signed graphs
Opis:
A graph whose edges are labeled either as positive or negative is called a signed graph. In this article, we extend the notion of composition of (unsigned) graphs (also called lexicographic product) to signed graphs. We employ Kronecker product of matrices to express the adjacency matrix of this product of two signed graphs and hence find its eigenvalues when the second graph under composition is net-regular. A signed graph is said to be net-regular if every vertex has constant net-degree, namely, the difference of the number of positive and negative edges incident with a vertex. We also characterize balance in signed graph composition and have some results on the Laplacian matrices of this product.
Źródło:
Discussiones Mathematicae Graph Theory; 2012, 32, 3; 507-516
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spectral study of alliances in graphs
Autorzy:
Rodríguez-Velazquez, Juan
Almira, Jose
Powiązania:
https://bibliotekanauki.pl/articles/743723.pdf
Data publikacji:
2007
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
defensive alliance
offensive alliance
dual alliance
domination
spectral radius
graph eigenvalues.
Opis:
In this paper we obtain several tight bounds on different types of alliance numbers of a graph, namely (global) defensive alliance number, global offensive alliance number and global dual alliance number. In particular, we investigate the relationship between the alliance numbers of a graph and its algebraic connectivity, its spectral radius, and its Laplacian spectral radius.
Źródło:
Discussiones Mathematicae Graph Theory; 2007, 27, 1; 143-157
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Displacement of Eigenvalues When Removing a Twin Vertex
Autorzy:
Briffa, Johann A.
Sciriha, Irene
Powiązania:
https://bibliotekanauki.pl/articles/31543314.pdf
Data publikacji:
2020-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
eigenvalues
perturbations
duplicate and co-duplicate vertices
threshold graph
nested split graph
Opis:
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.
Źródło:
Discussiones Mathematicae Graph Theory; 2020, 40, 2; 435-450
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Color energy of a unitary Cayley graph
Autorzy:
Adiga, Chandrashekar
Sampathkumar, E.
Sriraj, M.A.
Powiązania:
https://bibliotekanauki.pl/articles/31231988.pdf
Data publikacji:
2014-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
coloring of a graph
unitary Cayley graph
gcd-graph
color eigenvalues
color energy
Opis:
Let G be a vertex colored graph. The minimum number χ(G) of colors needed for coloring of a graph G is called the chromatic number. Recently, Adiga et al. [1] have introduced the concept of color energy of a graph Ec(G) and computed the color energy of few families of graphs with χ(G) colors. In this paper we derive explicit formulas for the color energies of the unitary Cayley graph Xn, the complement of the colored unitary Cayley graph $\overline{(Xn)c}$ and some gcd-graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 4; 707-721
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-11 z 11

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