Results 11 to 20 of about 514 (184)
Homomorphism–homogeneous graphs [PDF]
Journal of Graph Theory, 2010 AbstractWe answer two open questions posed by Cameron and Nesetril concerning homomorphism–homogeneous graphs. In particular we show, by giving a characterization of these graphs, that extendability to monomorphism or to homomorphism leads to the same class of graphs when defining homomorphism–homogeneity.
Momchil Rusinov, Pascal Schweitzer
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Graph Powers and Graph Homomorphisms [PDF]
The Electronic Journal of Combinatorics, 2010 In this paper, we investigate some basic properties of fractional powers. In this regard, we show that for any non-bipartite graph $G$ and positive rational numbers ${2r+1\over 2s+1} < {2p+1\over 2q+1}$, we have $G^{2r+1\over 2s+1} < G^{2p+1\over 2q+1}$. Next, we study the power thickness of $G$, that is, the supremum of rational numbers ${2r+
Hossein Hajiabolhassan, Ali Taherkhani
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Reconfiguring graph homomorphisms on the sphere [PDF]
European Journal of Combinatorics, 2020 Given a loop-free graph $H$, the reconfiguration problem for homomorphisms to $H$ (also called $H$-colourings) asks: given two $H$-colourings $f$ of $g$ of a graph $G$, is it possible to transform $f$ into $g$ by a sequence of single-vertex colour changes such that every intermediate mapping is an $H$-colouring?
Jae-Baek Lee +2 more
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Ideals of Graph Homomorphisms [PDF]
Annals of Combinatorics, 2012 In combinatorial commutative algebra and algebraic statistics many toric ideals are constructed from graphs. Keeping the categorical structure of graphs in mind we give previous results a more functorial context and generalize them by introducing the ideals of graph homomorphisms.
Engström Alexander, Norén Patrik
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The undecidability of joint embedding and joint homomorphism for hereditary graph classes [PDF]
Discrete Mathematics & Theoretical Computer Science, 2019 We prove that the joint embedding property is undecidable for hereditary graph classes, via a reduction from the tiling problem. The proof is then adapted to show the undecidability of the joint homomorphism property as well.
Samuel Braunfeld
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Extremal graphs for homomorphisms [PDF]
Journal of Graph Theory, 2011 Summary: The study of graph homomorphisms has a long and distinguished history, with applications in many areas of graph theory. There has been recent interest in counting homomorphisms, and in particular on the question of finding upper bounds for the number of homomorphisms from a graph \(G\) into a fixed image graph \(H\).
Jonathan Cutler, A. J. Radcliffe
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Homomorphisms into Loop-Threshold Graphs [PDF]
The Electronic Journal of Combinatorics, 2020 Many problems in extremal graph theory correspond to questions involving homomorphisms into a fixed image graph. Recently, there has been interest in maximizing the number of homomorphisms from graphs with a fixed number of vertices and edges into small image graphs.
Jonathan Cutler, Nicholas Kass
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Graph homomorphism revisited for graph matching [PDF]
Proceedings of the VLDB Endowment, 2010 In a variety of emerging applications one needs to decide whether a graph G matches another G p , i.e. , whether G has a topological structure similar to that of G p
Wenfei Fan +4 more
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Homomorphically Full Oriented Graphs
Discrete Mathematics & Theoretical Computer Science, 2023 Homomorphically full graphs are those for which every homomorphic image is isomorphic to a subgraph. We extend the definition of homomorphically full to oriented graphs in two different ways. For the first of these, we show that homomorphically full oriented graphs arise as quasi-transitive orientations of homomorphically full graphs.
Thomas Bellitto +2 more
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Action graph of a semigroup act & its functorial connection [PDF]
Categories and General Algebraic Structures with Applications, 2023 In this paper we define C-induced action graph G(S,a,C;A) corresponding to a semigroup act (S,a,A) and a subset C of S. This generalizes many interesting graphs including Cayley Graph of groups and semigroups, Transformation Graphs (TRAG), Group Action ...
Promit Mukherjee +2 more
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