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Wyszukujesz frazę "Semanišin, Gabriel" wg kryterium: Autor


Wyświetlanie 1-10 z 10
Tytuł:
On some variations of extremal graph problems
Autorzy:
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/972027.pdf
Data publikacji:
1997
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
hereditary properties of graphs
maximal graphs
extremal graphs
saturated graphs
Opis:
A set P of graphs is termed hereditary property if and only if it contains all subgraphs of any graph G belonging to P. A graph is said to be maximal with respect to a hereditary property P (shortly P-maximal) whenever it belongs to P and none of its proper supergraphs of the same order has the property P. A graph is P-extremal if it has a the maximum number of edges among all P-maximal graphs of given order. The number of its edges is denoted by ex(n, P). If the number of edges of a P-maximal graph is minimum, then the graph is called P-saturated and its number of edges is denoted by sat(n, P).
In this paper, we consider two famous problems of extremal graph theory. We shall translate them into the language of P-maximal graphs and utilize the properties of the lattice of all hereditary properties in order to establish some general bounds and particular results. Particularly, we shall investigate the behaviour of sat(n,P) and ex(n,P) in some interesting intervals of the mentioned lattice.
Źródło:
Discussiones Mathematicae Graph Theory; 1997, 17, 1; 67-76
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On generating sets of induced-hereditary properties
Autorzy:
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/743561.pdf
Data publikacji:
2002
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
induced-hereditary property of graphs
additivity
reducibility
generating sets
maximal graphs
unique factorization
Opis:
A natural generalization of the fundamental graph vertex-colouring problem leads to the class of problems known as generalized or improper colourings. These problems can be very well described in the language of reducible (induced) hereditary properties of graphs. It turned out that a very useful tool for the unique determination of these properties are generating sets. In this paper we focus on the structure of specific generating sets which provide the base for the proof of The Unique Factorization Theorem for induced-hereditary properties of graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2002, 22, 1; 183-192
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Maximum Semi-Matching Problem in Bipartite Graphs
Autorzy:
Katrenič, Ján
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/30146433.pdf
Data publikacji:
2013-07-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
semi-matching
quasi-matching
bipartite graph
computational complexity
Opis:
An $(f, g)$-semi-matching in a bipartite graph $ G = (U \cup V, E) $ is a set of edges $ M \subseteq E $ such that each vertex $ u \in U $ is incident with at most $f(u)$ edges of $M$, and each vertex $v \in V$ is incident with at most $g(v)$ edges of $M$. In this paper we give an algorithm that for a graph with $n$ vertices and $m$ edges, $n \leq m$, constructs a maximum $(f, g)$-semi-matching in running time $O(m \cdot $ $ min\{ \sqrt{\Sigma_{u \in U} f(u)}, $ $ \sqrt{ \Sigma_{v \in V} g(v) } \})$. Using the reduction of [5] our result on maximum $(f, g)$-semi-matching problem directly implies an algorithm for the optimal semi-matching problem with running time $ O( \sqrt{n} m \log n ) $.
Źródło:
Discussiones Mathematicae Graph Theory; 2013, 33, 3; 559-569
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Unique factorization theorem for object-systems
Autorzy:
Mihók, Peter
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/743977.pdf
Data publikacji:
2011
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
object-system
unique factorization
graph
hypergraph
formal concept analysis
Opis:
The concept of an object-system is a common generalization of simple graph, digraph and hypergraph. In the theory of generalised colourings of graphs, the Unique Factorization Theorem (UFT) for additive induced-hereditary properties of graphs provides an analogy of the well-known Fundamental Theorem of Arithmetics. The purpose of this paper is to present UFT for object-systems. This result generalises known UFT for additive induced-hereditary and hereditary properties of graphs and digraphs. Formal Concept Analysis is applied in the proof.
Źródło:
Discussiones Mathematicae Graph Theory; 2011, 31, 3; 559-575
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On universal graphs for hom-properties
Autorzy:
Mihók, Peter
Miškuf, Jozef
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/744408.pdf
Data publikacji:
2009
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
universal graph
weakly universal graph
hom-property
core
Opis:
A graph property is any isomorphism closed class of simple graphs. For a simple finite graph H, let → H denote the class of all simple countable graphs that admit homomorphisms to H, such classes of graphs are called hom-properties. Given a graph property , a graph G ∈ is universal in if each member of is isomorphic to an induced subgraph of G. In particular, we consider universal graphs in → H and we give a new proof of the existence of a universal graph in → H, for any finite graph H.
Źródło:
Discussiones Mathematicae Graph Theory; 2009, 29, 2; 401-409
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Graphs maximal with respect to hom-properties
Autorzy:
Kratochvíl, Jan
Mihók, Peter
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/971980.pdf
Data publikacji:
1997
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
hom-property of graphs
hereditary property of graphs
maximal graphs
Opis:
For a simple graph H, →H denotes the class of all graphs that admit homomorphisms to H (such classes of graphs are called hom-properties). We investigate hom-properties from the point of view of the lattice of hereditary properties. In particular, we are interested in characterization of maximal graphs belonging to →H. We also provide a description of graphs maximal with respect to reducible hom-properties and determine the maximum number of edges of graphs belonging to →H.
Źródło:
Discussiones Mathematicae Graph Theory; 1997, 17, 1; 77-88
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Maximal graphs with respect to hereditary properties
Autorzy:
Broere, Izak
Frick, Marietjie
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/972029.pdf
Data publikacji:
1997
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
hereditary property of graphs
maximal graphs
vertex partition
Opis:
A property of graphs is a non-empty set of graphs. A property P is called hereditary if every subgraph of any graph with property P also has property P. Let P₁, ...,Pₙ be properties of graphs. We say that a graph G has property P₁∘...∘Pₙ if the vertex set of G can be partitioned into n sets V₁, ...,Vₙ such that the subgraph of G induced by V_i has property $P_i$; i = 1,..., n. A hereditary property R is said to be reducible if there exist two hereditary properties P₁ and P₂ such that R = P₁∘P₂. If P is a hereditary property, then a graph G is called P- maximal if G has property P but G+e does not have property P for every e ∈ E([G̅]). We present some general results on maximal graphs and also investigate P-maximal graphs for various specific choices of P, including reducible hereditary properties.
Źródło:
Discussiones Mathematicae Graph Theory; 1997, 17, 1; 51-66
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Generalized ramsey theory and decomposable properties of graphs
Autorzy:
Burr, Stefan
Jacobson, Michael
Mihók, Peter
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/744152.pdf
Data publikacji:
1999
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
hereditary properties
additivity
reducibility
decomposability
Ramsey number
graph invariants
Opis:
In this paper we translate Ramsey-type problems into the language of decomposable hereditary properties of graphs. We prove a distributive law for reducible and decomposable properties of graphs. Using it we establish some values of graph theoretical invariants of decomposable properties and show their correspondence to generalized Ramsey numbers.
Źródło:
Discussiones Mathematicae Graph Theory; 1999, 19, 2; 199-217
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some Variations of Perfect Graphs
Autorzy:
Dettlaff, Magda
Lemańska, Magdalena
Semanišin, Gabriel
Zuazua, Rita
Powiązania:
https://bibliotekanauki.pl/articles/31340821.pdf
Data publikacji:
2016-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
k-path vertex cover
distance k-domination number
perfect graphs
Opis:
We consider (ψk−γk−1)-perfect graphs, i.e., graphs G for which ψk(H) = γk−1(H) for any induced subgraph H of G, where ψk and γk−1 are the k-path vertex cover number and the distance (k − 1)-domination number, respectively. We study (ψk−γk−1)-perfect paths, cycles and complete graphs for k ≥ 2. Moreover, we provide a complete characterisation of (ψ2 − γ1)- perfect graphs describing the set of its forbidden induced subgraphs and providing the explicit characterisation of the structure of graphs belonging to this family.
Źródło:
Discussiones Mathematicae Graph Theory; 2016, 36, 3; 661-668
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A survey of hereditary properties of graphs
Autorzy:
Borowiecki, Mieczysław
Broere, Izak
Frick, Marietjie
Mihók, Peter
Semanišin, Gabriel
Powiązania:
https://bibliotekanauki.pl/articles/971986.pdf
Data publikacji:
1997
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
hereditary property of graphs
vertex partition
reducible property
graph invariants
complexity
Opis:
In this paper we survey results and open problems on the structure of additive and hereditary properties of graphs. The important role of vertex partition problems, in particular the existence of uniquely partitionable graphs and reducible properties of graphs in this structure is emphasized. Many related topics, including questions on the complexity of related problems, are investigated.
Źródło:
Discussiones Mathematicae Graph Theory; 1997, 17, 1; 5-50
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-10 z 10

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