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Tytuł:
Graph Operations and Neighborhood Polynomials
Autorzy:
Alipour, Maryam
Tittmann, Peter
Powiązania:
https://bibliotekanauki.pl/articles/32083862.pdf
Data publikacji:
2021-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
neighborhood complex
neighborhood polynomial
domination polynomial
graph operations
graph degeneracy
Opis:
The neighborhood polynomial of graph G is the generating function for the number of vertex subsets of G of which the vertices have a common neighbor in G. In this paper, we investigate the behavior of this polynomial under several graph operations. Specifically, we provide an explicit formula for the neighborhood polynomial of the graph obtained from a given graph G by vertex attachment. We use this result to propose a recursive algorithm for the calculation of the neighborhood polynomial. Finally, we prove that the neighborhood polynomial can be found in polynomial-time in the class of k-degenerate graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 3; 697-711
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Note on the Permanental Roots of Bipartite Graphs
Autorzy:
Zhang, Heping
Liu, Shunyi
Li, Wei
Powiązania:
https://bibliotekanauki.pl/articles/30147218.pdf
Data publikacji:
2014-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
permanent
permanental polynomial
permanental roots
Opis:
It is well-known that any graph has all real eigenvalues and a graph is bipartite if and only if its spectrum is symmetric with respect to the origin. We are interested in finding whether the permanental roots of a bipartite graph G have symmetric property as the spectrum of G. In this note, we show that the permanental roots of bipartite graphs are symmetric with respect to the real and imaginary axes. Furthermore, we prove that any graph has no negative real permanental root, and any graph containing at least one edge has complex permanental roots.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 1; 49-56
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chromatic polynomials of mixed hypercycles
Autorzy:
Allagan, Julian A.
Slutzky, David
Powiązania:
https://bibliotekanauki.pl/articles/30148312.pdf
Data publikacji:
2014-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
hypercycle
mixed hypergraph
chromatic polynomial
Opis:
We color the vertices of each of the edges of a C-hypergraph (or cohypergraph) in such a way that at least two vertices receive the same color and in every proper coloring of a $\mathcal{B}$-hypergraph (or bihypergraph), we forbid the cases when the vertices of any of its edges are colored with the same color (monochromatic) or when they are all colored with distinct colors (rainbow). In this paper, we determined explicit formulae for the chromatic polynomials of $\mathcal{C}$-hypercycles and $\mathcal{B}$-hypercycles.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 3; 547-558
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bipartition Polynomials, the Ising Model, and Domination in Graphs
Autorzy:
Dod, Markus
Kotek, Tomer
Preen, James
Tittmann, Peter
Powiązania:
https://bibliotekanauki.pl/articles/31339472.pdf
Data publikacji:
2015-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
domination
Ising model
graph polynomial
Opis:
This paper introduces a trivariate graph polynomial that is a common generalization of the domination polynomial, the Ising polynomial, the matching polynomial, and the cut polynomial of a graph. This new graph polynomial, called the bipartition polynomial, permits a variety of interesting representations, for instance as a sum ranging over all spanning forests. As a consequence, the bipartition polynomial is a powerful tool for proving properties of other graph polynomials and graph invariants. We apply this approach to show that, analogously to the Tutte polynomial, the Ising polynomial introduced by Andrén and Markström in [3], can be represented as a sum over spanning forests.
Źródło:
Discussiones Mathematicae Graph Theory; 2015, 35, 2; 335-353
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Graphs Whose Permanental Polynomials Are Symmetric
Autorzy:
Li, Wei
Powiązania:
https://bibliotekanauki.pl/articles/31342428.pdf
Data publikacji:
2018-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
permanental polynomial
rooted product
matching
Opis:
The permanental polynomial $ \pi (G,x) = \Sigma_{i=0}^n b_i x^{n − i} $ of a graph G is symmetric if $ b_i = b_n−i $ for each $i$. In this paper, we characterize the graphs with symmetric permanental polynomials. Firstly, we introduce the rooted product $ H(K) $ of a graph $ H $ by a graph $ K $, and provide a way to compute the permanental polynomial of the rooted product $ H(K) $. Then we give a sufficient and necessary condition for the symmetric polynomial, and we prove that the permanental polynomial of a graph $ G $ is symmetric if and only if $ G $ is the rooted product of a graph by a path of length one.
Źródło:
Discussiones Mathematicae Graph Theory; 2018, 38, 1; 233-243
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mean value for the matching and dominating polynomial
Autorzy:
Arocha, Jorge
Llano, Bernardo
Powiązania:
https://bibliotekanauki.pl/articles/743687.pdf
Data publikacji:
2000
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
matching
matching polynomial
dominating set
Opis:
The mean value of the matching polynomial is computed in the family of all labeled graphs with n vertices. We introduce the dominating polynomial of a graph whose coefficients enumerate the dominating sets for a graph and study some properties of the polynomial. The mean value of this polynomial is determined in a certain special family of bipartite digraphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2000, 20, 1; 57-69
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An inductive proof of Whitneys Broken Circuit Theorem
Autorzy:
Dohmen, Klaus
Powiązania:
https://bibliotekanauki.pl/articles/743963.pdf
Data publikacji:
2011
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
chromatic polynomial
broken circuit
induction
Opis:
We present a new proof of Whitney's broken circuit theorem based on induction on the number of edges and the deletion-contraction formula.
Źródło:
Discussiones Mathematicae Graph Theory; 2011, 31, 3; 509-515
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:
Conditions for β-perfectness
Autorzy:
Keijsper, Judith
Tewes, Meike
Powiązania:
https://bibliotekanauki.pl/articles/743553.pdf
Data publikacji:
2002
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
chromatic number
colouring number
polynomial time
Opis:
A β-perfect graph is a simple graph G such that χ(G') = β(G') for every induced subgraph G' of G, where χ(G') is the chromatic number of G', and β(G') is defined as the maximum over all induced subgraphs H of G' of the minimum vertex degree in H plus 1 (i.e., δ(H)+1). The vertices of a β-perfect graph G can be coloured with χ(G) colours in polynomial time (greedily).
The main purpose of this paper is to give necessary and sufficient conditions, in terms of forbidden induced subgraphs, for a graph to be β-perfect. We give new sufficient conditions and make improvements to sufficient conditions previously given by others. We also mention a necessary condition which generalizes the fact that no β-perfect graph contains an even hole.
Źródło:
Discussiones Mathematicae Graph Theory; 2002, 22, 1; 123-148
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some Results on the Independence Polynomial of Unicyclic Graphs
Autorzy:
Oboudi, Mohammad Reza
Powiązania:
https://bibliotekanauki.pl/articles/31342319.pdf
Data publikacji:
2018-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
independence polynomial
independent set
unicyclic graphs
Opis:
Let $G$ be a simple graph on $n$ vertices. An independent set in a graph is a set of pairwise non-adjacent vertices. The independence polynomial of $G$ is the polynomial $ I(G,x)= \Sigma_{k=0}^n s(G,k)x^k $, where $s(G, k)$ is the number of independent sets of $G$ with size $k$ and $s(G, 0) = 1$. A unicyclic graph is a graph containing exactly one cycle. Let $ C_n $ be the cycle on $n$ vertices. In this paper we study the independence polynomial of unicyclic graphs. We show that among all connected unicyclic graphs $G$ on $n$ vertices (except two of them), $ I(G, t) > I(C_n, t)$ for sufficiently large $t$. Finally for every $ n \ge 3 $ we find all connected graphs $H$ such that $I(H, x) = I(C_n, x) $.
Źródło:
Discussiones Mathematicae Graph Theory; 2018, 38, 2; 515-524
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An attractive class of bipartite graphs
Autorzy:
Boliac, Rodica
Lozin, Vadim
Powiązania:
https://bibliotekanauki.pl/articles/743515.pdf
Data publikacji:
2001
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
bipartite graphs
structural characterization
polynomial algorithm
Opis:
In this paper we propose a structural characterization for a class of bipartite graphs defined by two forbidden induced subgraphs. We show that the obtained characterization leads to polynomial-time algorithms for several problems that are NP-hard in general bipartite graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2001, 21, 2; 293-301
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Per-Spectral Characterizations Of Some Bipartite Graphs
Autorzy:
Wu, Tingzeng
Zhang, Heping
Powiązania:
https://bibliotekanauki.pl/articles/31341599.pdf
Data publikacji:
2017-11-27
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
permanent
permanental polynomial
per-spectrum
cospectral
Opis:
A graph is said to be characterized by its permanental spectrum if there is no other non-isomorphic graph with the same permanental spectrum. In this paper, we investigate when a complete bipartite graph Kp,p with some edges deleted is determined by its permanental spectrum. We first prove that a graph obtained from Kp,p by deleting all edges of a star K1,l, provided l < p, is determined by its permanental spectrum. Furthermore, we show that all graphs with a perfect matching obtained from Kp,p by removing five or fewer edges are determined by their permanental spectra.
Źródło:
Discussiones Mathematicae Graph Theory; 2017, 37, 4; 935-951
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On chromaticity of graphs
Autorzy:
Łazuka, Ewa
Powiązania:
https://bibliotekanauki.pl/articles/971927.pdf
Data publikacji:
1995
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
chromatic polynomial
chromatically equivalent graphs
chromatic characterization
Opis:
In this paper we obtain the explicit formulas for chromatic polynomials of cacti. From the results relating to cacti we deduce the analogous formulas for the chromatic polynomials of n-gon-trees. Besides, we characterize unicyclic graphs by their chromatic polynomials. We also show that the so-called clique-forest-like graphs are chromatically equivalent.
Źródło:
Discussiones Mathematicae Graph Theory; 1995, 15, 1; 19-31
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chromatic polynomials of hypergraphs
Autorzy:
Borowiecki, Mieczysław
Łazuka, Ewa
Powiązania:
https://bibliotekanauki.pl/articles/743817.pdf
Data publikacji:
2000
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
chromatic polynomial
chromatically unique hypergraphs
chromatic characterization
Opis:
In this paper we present some hypergraphs which are chromatically characterized by their chromatic polynomials. It occurs that these hypergraphs are chromatically unique. Moreover we give some equalities for the chromatic polynomials of hypergraphs generalizing known results for graphs and hypergraphs of Read and Dohmen.
Źródło:
Discussiones Mathematicae Graph Theory; 2000, 20, 2; 293-301
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Extremal Matching Energy of Complements of Trees
Autorzy:
Wu, Tingzeng
Yan, Weigen
Zhang, Heping
Powiązania:
https://bibliotekanauki.pl/articles/31340889.pdf
Data publikacji:
2016-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
matching polynomial
matching energy
Hosoya index
energy
Opis:
Gutman and Wagner proposed the concept of the matching energy which is defined as the sum of the absolute values of the zeros of the matching polynomial of a graph. And they pointed out that the chemical applications of matching energy go back to the 1970s. Let $T$ be a tree with n vertices. In this paper, we characterize the trees whose complements have the maximal, second-maximal and minimal matching energy. Furthermore, we determine the trees with edge-independence number p whose complements have the minimum matching energy for $ p = 1, 2, . . ., \floor{ n/2 } $. When we restrict our consideration to all trees with a perfect matching, we determine the trees whose complements have the second-maximal matching energy.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 3; 505-521
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł

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