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On partitions of hereditary properties of graphs

Mieczysław Borowiecki, Anna Fiedorowicz (2006)

Discussiones Mathematicae Graph Theory

In this paper a concept 𝓠-Ramsey Class of graphs is introduced, where 𝓠 is a class of bipartite graphs. It is a generalization of well-known concept of Ramsey Class of graphs. Some 𝓠-Ramsey Classes of graphs are presented (Theorem 1 and 2). We proved that 𝓣₂, the class of all outerplanar graphs, is not 𝓓₁-Ramsey Class (Theorem 3). This results leads us to the concept of acyclic reducible bounds for a hereditary property 𝓟 . For 𝓣₂ we found two bounds (Theorem 4). An improvement, in some sense,...

On properties of a graph that depend on its distance function

Ladislav Nebeský (2004)

Czechoslovak Mathematical Journal

If G is a connected graph with distance function d , then by a step in G is meant an ordered triple ( u , x , v ) of vertices of G such that d ( u , x ) = 1 and d ( u , v ) = d ( x , v ) + 1 . A characterization of the set of all steps in a connected graph was published by the present author in 1997. In Section 1 of this paper, a new and shorter proof of that characterization is presented. A stronger result for a certain type of connected graphs is proved in Section 2.

On sectional Newtonian graphs

Zening Fan, Suo Zhao (2020)

Czechoslovak Mathematical Journal

In this paper, we introduce the so-called sectional Newtonian graphs for univariate complex polynomials, and study some properties of those graphs. In particular, we list all possible sectional Newtonian graphs when the degrees of the polynomials are less than five, and also show that every stable gradient graph can be realized as a polynomial sectional Newtonian graph.

On some non-obvious connections between graphs and unary partial algebras

Konrad Pióro (2000)

Czechoslovak Mathematical Journal

In the present paper we generalize a few algebraic concepts to graphs. Applying this graph language we solve some problems on subalgebra lattices of unary partial algebras. In this paper three such problems are solved, other will be solved in papers [Pió I], [Pió II], [Pió III], [Pió IV]. More precisely, in the present paper first another proof of the following algebraic result from [Bar1] is given: for two unary partial algebras 𝐀 and 𝐁 , their weak subalgebra lattices are isomorphic if and only...

On super (a,d)-edge antimagic total labeling of certain families of graphs

P. Roushini Leely Pushpam, A. Saibulla (2012)

Discussiones Mathematicae Graph Theory

A (p, q)-graph G is (a,d)-edge antimagic total if there exists a bijection f: V(G) ∪ E(G) → {1, 2,...,p + q} such that the edge weights Λ(uv) = f(u) + f(uv) + f(v), uv ∈ E(G) form an arithmetic progression with first term a and common difference d. It is said to be a super (a, d)-edge antimagic total if the vertex labels are {1, 2,..., p} and the edge labels are {p + 1, p + 2,...,p + q}. In this paper, we study the super (a,d)-edge antimagic total labeling of special classes of graphs derived from...

On supermagic regular graphs

Jaroslav Ivančo (2000)

Mathematica Bohemica

A graph is called supermagic if it admits a labelling of the edges by pairwise different consecutive positive integers such that the sum of the labels of the edges incident with a vertex is independent of the particular vertex. Some constructions of supermagic labellings of regular graphs are described. Supermagic regular complete multipartite graphs and supermagic cubes are characterized.

On the Boolean function graph of a graph and on its complement

T. N. Janakiraman, S. Muthammai, M. Bhanumathi (2005)

Mathematica Bohemica

For any graph G , let V ( G ) and E ( G ) denote the vertex set and the edge set of G respectively. The Boolean function graph B ( G , L ( G ) , N I N C ) of G is a graph with vertex set V ( G ) ∪ E ( G ) and two vertices in B ( G , L ( G ) , N I N C ) are adjacent if and only if they correspond to two adjacent vertices of G , two adjacent edges of G or to a vertex and an edge not incident to it in G . For brevity, this graph is denoted by B 1 ( G ) . In this paper, structural properties of B 1 ( G ) and its complement including traversability and eccentricity properties are studied. In addition,...

On the complete digraphs which are simply disconnected.

Davide C. Demaria, José Carlos de Souza Kiihl (1991)

Publicacions Matemàtiques

Homotopic methods are employed for the characterization of the complete digraphs which are the composition of non-trivial highly regular tournaments.

On the computational complexity of (O,P)-partition problems

Jan Kratochvíl, Ingo Schiermeyer (1997)

Discussiones Mathematicae Graph Theory

We prove that for any additive hereditary property P > O, it is NP-hard to decide if a given graph G allows a vertex partition V(G) = A∪B such that G[A] ∈ 𝓞 (i.e., A is independent) and G[B] ∈ P.

On the existence of a cycle of length at least 7 in a (1,≤ 2)-twin-free graph

David Auger, Irène Charon, Olivier Hudry, Antoine Lobstein (2010)

Discussiones Mathematicae Graph Theory

We consider a simple, undirected graph G. The ball of a subset Y of vertices in G is the set of vertices in G at distance at most one from a vertex in Y. Assuming that the balls of all subsets of at most two vertices in G are distinct, we prove that G admits a cycle with length at least 7.

On the factorization of reducible properties of graphs into irreducible factors

P. Mihók, R. Vasky (1995)

Discussiones Mathematicae Graph Theory

A hereditary property R of graphs is said to be reducible if there exist hereditary properties P₁,P₂ such that G ∈ R if and only if the set of vertices of G can be partitioned into V(G) = V₁∪V₂ so that ⟨V₁⟩ ∈ P₁ and ⟨V₂⟩ ∈ P₂. The problem of the factorization of reducible properties into irreducible factors is investigated.

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