Results 31 to 40 of about 238 (165)
Graph Homomorphisms between Trees [PDF]
The Electronic Journal of Combinatorics, 2014 In this paper we study several problems concerning the number of homomorphisms of trees. We begin with an algorithm for the number of homomorphisms from a tree to any graph. By using this algorithm and some transformations on trees, we study various extremal problems about the number of homomorphisms of trees.
Csikvari, Peter, Lin, Zhicong
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A Homomorphic Polynomial for Oriented Graphs
The Electronic Journal of Combinatorics, 2023 In this article, we define a function that counts the number of (onto) homomorphisms of an oriented graph. We show that this function is always a polynomial and establish it as an extension of the notion of chromatic polynomials. We study algebraic properties of this function.
Sandip Das 0001 +3 more
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A digraph equation for homomorphic images
International Journal of Mathematics and Mathematical Sciences, 1986 The definitions of a homomorphism and a contraction of a graph are generalized to digraphs. Solutions are given to the graph equation ϕ(D)¯=θϕ(D¯).
Robert D. Girse, Richard A. Gillman
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Dichotomy Theorems for Homomorphism Polynomials of Graph Classes
Journal of Graph Algorithms and Applications, 2016 In this paper, we will show dichotomy theorems for the computation of polynomials corresponding to evaluation of graph homomorphisms in Valiant's model. We are given a fixed graph H and want to find all graphs, from some graph class, homomorphic
Christian Engels
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Discrete Applied Mathematics, 1996 As the title of this paper shows the two authors deal with homomorphically full graphs. After having given the precise definition of the concept of a homomorphically full graph and the proof of two very interesting properties of homomorphically full graphs the two authors succeed in proving the main result of this paper saying the equivalence of six ...
Richard C. Brewster, Gary MacGillivray
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Homomorphisms of Sparse Signed Graphs [PDF]
The Electronic Journal of Combinatorics, 2020 The notion of homomorphism of signed graphs, introduced quite recently, provides better interplay with the notion of minor and is thus of high importance in graph coloring. A newer, but equivalent, definition of homomorphisms of signed graphs, proposed jointly by the second and third authors of this paper and Thomas Zaslavsky, leads to a basic no ...
Charpentier, Clément +2 more
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Homomorphisms and related contractions of graphs
International Journal of Mathematics and Mathematical Sciences, 1988 For every homomorphism ϕ of a graph G there exists a contraction θϕ on G¯, the complement of G. Here we study the graph equation ϕ(G)=θϕ(G¯). In the course of our work we show that Hadwiger's Conjecture is true for every self-complementary graph.
Robert D. Girse, Richard A. Gillman
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Intuitionistic Fuzzy Graphs with Categorical Properties
Fuzzy Information and Engineering, 2015 The main purpose of this paper is to show the rationality of some operations, defined or to be defined, on intuitionistic fuzzy graphs. Firstly, three kinds of new product operations (called direct product, lexicographic product, and strong product) are ...
Hossein Rashmanlou +3 more
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Retractions and Homomorphisms on Some Operations of Graphs
Journal of Mathematics, 2018 The aim of the present article is to introduce and study a new type of operations on graph, namely, edge graph. The relation between the homomorphisms and retractions on edge graphs is deduced.
M. Abu-Saleem
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Complex Intuitionistic Fuzzy Graphs with Application in Cellular Network Provider Companies
Mathematics, 2019 In recent years, a mathematical approach of blending different aspects is on the way, which as a result gives a more generalized approach. Following the above mathematical approach, we combine two very powerful techniques, namely complex intuitionistic ...
Naveed Yaqoob +3 more
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