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Wyszukujesz frazę "Sano, Yoshio" wg kryterium: Autor


Wyświetlanie 1-4 z 4
Tytuł:
On the Hypercompetition Numbers of Hypergraphs with Maximum Degree at Most Two
Autorzy:
Sano, Yoshio
Powiązania:
https://bibliotekanauki.pl/articles/31339316.pdf
Data publikacji:
2015-08-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
digraph
competition hypergraph
hypercompetition number
Opis:
In this note, we give an easy and short proof for the theorem by Park and Kim stating that the hypercompetition numbers of hypergraphs with maximum degree at most two is at most two.
Źródło:
Discussiones Mathematicae Graph Theory; 2015, 35, 3; 595-598
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The niche graphs of interval orders
Autorzy:
Park, Jeongmi
Sano, Yoshio
Powiązania:
https://bibliotekanauki.pl/articles/30148237.pdf
Data publikacji:
2014-05-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
competition graph
niche graph
semiorder
interval order
Opis:
The niche graph of a digraph $D$ is the (simple undirected) graph which has the same vertex set as $D$ and has an edge between two distinct vertices $x$ and $y$ if and only if $N_D^+(x) ∩ N_D^+(y) ≠ ∅ or N_D^−(x) ∩ N_D^−(y) ≠ ∅$, where $N_D^+(x)$ (resp. $N_D^−(x)$) is the set of out-neighbors (resp. in-neighbors) of $x$ in $D$. A digraph $D = (V,A)$ is called a semiorder (or a unit interval order) if there exist a real-valued function $f : V → \mathbb{R}$ on the set $V$ and a positive real number $δ ∈ \mathbb{R}$ such that $(x, y) ∈ A$ if and only if $f(x) > f(y)+δ$. A digraph $D = (V,A)$ is called an interval order if there exists an assignment $J$ of a closed real interval $J(x) ⊂ \mathbb{R}$ to each vertex $x ∈ V$ such that $(x, y) ∈ A$ if and only if $min J(x) > max J(y)$. Kim and Roberts characterized the competition graphs of semiorders and interval orders in 2002, and Sano characterized the competition-common enemy graphs of semiorders and interval orders in 2010. In this note, we give characterizations of the niche graphs of semiorders and interval orders
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 2; 353-359
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Phylogeny Graphs of Doubly Partial Orders
Autorzy:
Park, Boram
Sano, Yoshio
Powiązania:
https://bibliotekanauki.pl/articles/29551728.pdf
Data publikacji:
2013-09-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
competition graph
phylogeny graph
doubly partial order
interval graph
Opis:
The competition graph of a doubly partial order is known to be an interval graph. The CCE graph and the niche graph of a doubly partial order are also known to be interval graphs if the graphs do not contain a cycle of length four and three as an induced subgraph, respectively. Phylogeny graphs are variant of competition graphs. The phylogeny graph P(D) of a digraph D is the (simple undirected) graph defined by V (P(D)) := V (D) and E(P(D)) := {xy | N+D (x) ∩ N+D(y) ¹ ⊘ } ⋃ {xy | (x,y) ∈ A(D)}, where N+D(x):= {v ∈ V(D) | (x,v) ∈ A (D)}. In this note, we show that the phylogeny graph of a doubly partial order is an interval graph. We also show that, for any interval graph G̃, there exists an interval graph G such that G̃ contains the graph G as an induced subgraph and that G̃ is the phylogeny graph of a doubly partial order.
Źródło:
Discussiones Mathematicae Graph Theory; 2013, 33, 4; 657-664
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The competition numbers of Johnson graphs
Autorzy:
Kim, Suh-Ryung
Park, Boram
Sano, Yoshio
Powiązania:
https://bibliotekanauki.pl/articles/744040.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
competition graph
competition number
edge clique cover
Johnson graph
Opis:
The competition graph of a digraph D is a graph which has the same vertex set as D and has an edge between two distinct vertices x and y if and only if there exists a vertex v in D such that (x,v) and (y,v) are arcs of D. For any graph G, G together with sufficiently many isolated vertices is the competition graph of some acyclic digraph. The competition number k(G) of a graph G is defined to be the smallest number of such isolated vertices. In general, it is hard to compute the competition number k(G) for a graph G and to characterize all graphs with given competition number k has been one of the important research problems in the study of competition graphs.
The Johnson graph J(n,d) has the vertex set ${v_X | X ∈ \binom{[n]}{d}$, where $\binom{[n]}{d}$ denotes the set of all d-subsets of an n-set [n] = {1,..., n}, and two vertices $v_{X₁}$ and $v_{X₂}$ are adjacent if and only if |X₁ ∩ X₂| = d - 1. In this paper, we study the edge clique number and the competition number of J(n,d). Especially we give the exact competition numbers of J(n,2) and J(n,3).
Źródło:
Discussiones Mathematicae Graph Theory; 2010, 30, 3; 449-459
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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