Temat: Homomorphism - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Distinguishing graphs by the number of homomorphisms
Autorzy:: Fisk, Steve
Powiązania:: https://bibliotekanauki.pl/articles/971917.pdf
Data publikacji:: 1995
Wydawca:: Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:: graph homomorphism
chromatic number
Opis:: A homomorphism from one graph to another is a map that sends vertices to vertices and edges to edges. We denote the number of homomorphisms from G to H by |G → H|. If is a collection of graphs, we say that distinguishes graphs G and H if there is some member X of such that |G → X | ≠ |H → X|. is a distinguishing family if it distinguishes all pairs of graphs.
We show that various collections of graphs are a distinguishing family.
Źródło:: Discussiones Mathematicae Graph Theory; 1995, 15, 1; 73-75
2083-5892
Pojawia się w:: Discussiones Mathematicae Graph Theory
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: On maximal finite antichains in the homomorphism order of directed graphs
Autorzy:: Nesetril, Jaroslav
Tardif, Claude
Powiązania:: https://bibliotekanauki.pl/articles/743175.pdf
Data publikacji:: 2003
Wydawca:: Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:: chromatic number
homomorphism duality
Opis:: We show that the pairs ${T,D_T}$ where T is a tree and $D_T$ its dual are the only maximal antichains of size 2 in the category of directed graphs endowed with its natural homomorphism ordering.
Źródło:: Discussiones Mathematicae Graph Theory; 2003, 23, 2; 325-332
2083-5892
Pojawia się w:: Discussiones Mathematicae Graph Theory
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: The Quest for A Characterization of Hom-Properties of Finite Character
Autorzy:: Broere, Izak
Matsoha, Moroli D.V.
Heidema, Johannes
Powiązania:: https://bibliotekanauki.pl/articles/31340894.pdf
Data publikacji:: 2016-05-01
Wydawca:: Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:: (countable) graph
homomorphism (of graphs)
property of graphs
hom-property
(finitely-)induced-hereditary property
finitely determined property
(weakly) finite character
axiomatizable property
compactness theorems
core
connectedness
chromatic number
clique number
independence number
dominating set
Opis:: A graph property is a set of (countable) graphs. A homomorphism from a graph $ G $ to a graph $ H $ is an edge-preserving map from the vertex set of $ G $ into the vertex set of $ H $; if such a map exists, we write $ G \rightarrow H $. Given any graph $ H $, the hom-property $ \rightarrow H $ is the set of $ H $-colourable graphs, i.e., the set of all graphs $ G $ satisfying $ G \rightarrow H $. A graph property $ mathcal{P} $ is of finite character if, whenever we have that $ F \in \mathcal{P} $ for every finite induced subgraph $ F $ of a graph $ G $, then we have that $ G \in \mathcal{P} $ too. We explore some of the relationships of the property attribute of being of finite character to other property attributes such as being finitely-induced-hereditary, being finitely determined, and being axiomatizable. We study the hom-properties of finite character, and prove some necessary and some sufficient conditions on $ H $ for $ \rightarrow H $ to be of finite character. A notable (but known) sufficient condition is that $ H $ is a finite graph, and our new model-theoretic proof of this compactness result extends from hom-properties to all axiomatizable properties. In our quest to find an intrinsic characterization of those $ H $ for which $ \rightarrow H $ is of finite character, we find an example of an infinite connected graph with no finite core and chromatic number 3 but with hom-property not of finite character.
Źródło:: Discussiones Mathematicae Graph Theory; 2016, 36, 2; 479-500
2083-5892
Pojawia się w:: Discussiones Mathematicae Graph Theory
Dostawca treści:: Biblioteka Nauki

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