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Rok 2023
  • Restrained differential of a graph
    Publikacja

    - Discussiones Mathematicae Graph Theory - Rok 2023

    Given a graph $G=(V(G), E(G))$ and a vertex $v\in V(G)$, the {open neighbourhood} of $v$ is defined to be $N(v)=\{u\in V(G) :\, uv\in E(G)\}$. The {external neighbourhood} of a set $S\subseteq V(G)$ is defined as $S_e=\left(\cup_{v\in S}N(v)\right)\setminus S$, while the \emph{restrained external neighbourhood} of $S$ is defined as $S_r=\{v\in S_e : N(v)\cap S_e\neq \varnothing\}$. The restrained differential of a graph $G$ is...

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Rok 2022
  • On proper (1,2)‐dominating sets in graphs
    Publikacja

    In 2008, Hedetniemi et al. introduced the concept of (1,)-domination and obtained some interesting results for (1,2) -domination. Obviously every (1,1) -dominating set of a graph (known as 2-dominating set) is (1,2) -dominating; to distinguish these concepts, we define a proper (1,2) -dominating set of a graph as follows: a subset is a proper (1,2) -dominating set of a graph if is (1,2) -dominating and it is not a (1,1) -dominating...

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  • Paired domination versus domination and packing number in graphs
    Publikacja

    Given a graph G = (V(G), E(G)), the size of a minimum dominating set, minimum paired dominating set, and a minimum total dominating set of a graph G are denoted by γ (G), γpr(G), and γt(G), respectively. For a positive integer k, a k-packing in G is a set S ⊆ V(G) such that for every pair of distinct vertices u and v in S, the distance between u and v is at least k + 1. The k-packing number is the order of a largest kpacking and...

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Rok 2021
  • Common Independence in Graphs
    Publikacja

    - Symmetry-Basel - Rok 2021

    Abstract: The cardinality of a largest independent set of G, denoted by α(G), is called the independence number of G. The independent domination number i(G) of a graph G is the cardinality of a smallest independent dominating set of G. We introduce the concept of the common independence number of a graph G, denoted by αc(G), as the greatest integer r such that every vertex of G belongs to some independent subset X of VG with |X|...

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  • Independent Domination Subdivision in Graphs
    Publikacja

    - GRAPHS AND COMBINATORICS - Rok 2021

    A set $S$ of vertices in a graph $G$ is a dominating set if every vertex not in $S$ is adjacent to a vertex in~$S$. If, in addition, $S$ is an independent set, then $S$ is an independent dominating set. The independent domination number $i(G)$ of $G$ is the minimum cardinality of an independent dominating set in $G$. The independent domination subdivision number $\sdi(G)$ is the minimum number of edges that must be subdivided (each...

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  • Secure Italian domination in graphs
    Publikacja

    - JOURNAL OF COMBINATORIAL OPTIMIZATION - Rok 2021

    An Italian dominating function (IDF) on a graph G is a function f:V(G)→{0,1,2} such that for every vertex v with f(v)=0, the total weight of f assigned to the neighbours of v is at least two, i.e., ∑u∈NG(v)f(u)≥2. For any function f:V(G)→{0,1,2} and any pair of adjacent vertices with f(v)=0 and u with f(u)>0, the function fu→v is defined by fu→v(v)=1, fu→v(u)=f(u)−1 and fu→v(x)=f(x) whenever x∈V(G)∖{u,v}. A secure Italian dominating...

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  • Some variants of perfect graphs related to the matching number, the vertex cover and the weakly connected domination number
    Publikacja

    Given two types of graph theoretical parameters ρ and σ, we say that a graph G is (σ, ρ)- perfect if σ(H) = ρ(H) for every non-trivial connected induced subgraph H of G. In this work we characterize (γw, τ )-perfect graphs, (γw, α′)-perfect graphs, and (α′, τ )-perfect graphs, where γw(G), τ (G) and α′(G) denote the weakly connected domination number, the vertex cover number and the matching number of G, respectively. Moreover,...

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Rok 2020
Rok 2019
  • Domination subdivision and domination multisubdivision numbers of graphs

    The domination subdivision number sd(G) of a graph G is the minimum number of edges that must be subdivided (where an edge can be subdivided at most once) in order to increase the domination number of G. It has been shown [10] that sd(T)<=3 for any tree T. We prove that the decision problem of the domination subdivision number is NP-complete even for bipartite graphs. For this reason we define the domination multisubdivision number...

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  • Graphs with equal domination and certified domination numbers
    Publikacja

    - Opuscula Mathematica - Rok 2019

    A setDof vertices of a graphG= (VG,EG) is a dominating set ofGif every vertexinVG−Dis adjacent to at least one vertex inD. The domination number (upper dominationnumber, respectively) ofG, denoted byγ(G) (Γ(G), respectively), is the cardinality ofa smallest (largest minimal, respectively) dominating set ofG. A subsetD⊆VGis calleda certified dominating set ofGifDis a dominating set ofGand every vertex inDhas eitherzero...

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  • On the super domination number of lexicographic product graphs
    Publikacja

    - DISCRETE APPLIED MATHEMATICS - Rok 2019

    The neighbourhood of a vertexvof a graphGis the setN(v) of all verticesadjacent tovinG. ForD⊆V(G) we defineD=V(G)\D. A setD⊆V(G) is called a super dominating set if for every vertexu∈D, there existsv∈Dsuch thatN(v)∩D={u}. The super domination number ofGis theminimum cardinality among all super dominating sets inG. In this article weobtain closed formulas and tight bounds for the super dominating number oflexicographic product...

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Rok 2018
Rok 2016
  • Edge subdivision and edge multisubdivision versus some domination related parameters in generalized corona graphs
    Publikacja

    - Opuscula Mathematica - Rok 2016

    Given a graph G= (V, E), the subdivision of an edge e=uv∈E(G) means the substitution of the edge e by a vertex x and the new edges ux and xv. The domination subdivision number of a graph G is the minimum number of edges of G which must be subdivided (where each edge can be subdivided at most once) in order to increase the domination number. Also, the domination multisubdivision number of G is the minimum number of subdivisions...

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  • Some variations of perfect graphs
    Publikacja

    - Discussiones Mathematicae Graph Theory - Rok 2016

    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...

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  • The convex domination subdivision number of a graph
    Publikacja

    Let G = (V;E) be a simple graph. A set D\subset V is a dominating set of G if every vertex in V - D has at least one neighbor in D. The distance d_G(u, v) between two vertices u and v is the length of a shortest (u, v)-path in G. An (u, v)-path of length d_G(u; v) is called an (u, v)-geodesic. A set X\subset V is convex in G if vertices from all (a, b)-geodesics belong to X for any two vertices a, b \in X. A set X is a convex dominating...

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  • Weakly convex domination subdivision number of a graph
    Publikacja

    - FILOMAT - Rok 2016

    A set X is weakly convex in G if for any two vertices a; b \in X there exists an ab–geodesic such that all of its vertices belong to X. A set X \subset V is a weakly convex dominating set if X is weakly convex and dominating. The weakly convex domination number \gamma_wcon(G) of a graph G equals the minimum cardinality of a weakly convex dominating set in G. The weakly convex domination subdivision number sd_wcon (G) is the minimum...

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Rok 2015
  • INFLUENCE OF A VERTEX REMOVING ON THE CONNECTED DOMINATION NUMBER – APPLICATION TO AD-HOC WIRELESS NETWORKS
    Publikacja

    - Rok 2015

    A minimum connected dominating set (MCDS) can be used as virtual backbone in ad-hoc wireless networks for efficient routing and broadcasting tasks. To find the MCDS is an NP- complete problem even in unit disk graphs. Many suboptimal algorithms are reported in the literature to find the MCDS using local information instead to use global network knowledge, achieving an important reduction in complexity. Since a wireless network...

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  • TOTAL DOMINATION MULTISUBDIVISION NUMBER OF A GRAPH
    Publikacja

    - Discussiones Mathematicae Graph Theory - Rok 2015

    The domination multisubdivision number of a nonempty graph G was defined in [3] as the minimum positive integer k such that there exists an edge which must be subdivided k times to increase the domination number of G. Similarly we define the total domination multisubdivision number msd_t (G) of a graph G and we show that for any connected graph G of order at least two, msd_t (G) ≤ 3. We show that for trees the total domination...

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Rok 2014
  • Bondage number of grid graphs
    Publikacja

    The bondage number b(G) of a nonempty graph G is the cardinality of a smallest set of edges whose removal from G results in a graph with domination number greater than the domination number of G. Here we study the bondage number of some grid-like graphs. In this sense, we obtain some bounds or exact values of the bondage number of some strong product and direct product of two paths.

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  • LICZBA PODZIAŁOWA DLA DOMINOWANIA W GRAFACH
    Publikacja

    - Rok 2014

    W PRACY ROZWAŻAMY 6 RODZAJÓW ZBIORÓW DOMINUJĄCYCH ORAZ LICZB ZWIĄZANYCH Z TYMI ZBIORAMI: KLASYCZNĄ LICZBĘ DOMINOWANIA, LICZBĘ DOMINOWANIA TOTALNEGO, PARAMI, SŁABO-SPÓJNEGO, 2-DOMINOWANIA I DOMINOWANIA WYPUKŁEGO. W PRACY ROZWAŻAMY WPŁYW TRZECH OPERACJI NA KRAWĘDZIE GRAFU: USUWANIE KRAWĘDZI Z GRAFU, JEDNOKROTNY PODZIAŁ PEWNEJ LICZBY KRAWĘDZI I PODZIAŁ WIELOKROTNY JEDNEJ KRAWĘDZI. BADAMY ZWIĄZKI TYCH OPERACJI Z ROZWAŻANYMI LICZBAMI...

Rok 2012
Rok 2010
Rok 2009
  • Planarność i zewnętrzna planarność grafów
    Publikacja

    - Rok 2009

    Niech G będzie niepustym grafem prostym. Graf, który można przedstawić na płaszczyźnie w taki sposób, że żadne dwie krawędzie nie przecinają się nazywamy grafem płaskim, natomiast graf nazywamy planarnym, gdy jest on izomorficzny do grafu płaskiego. Jeśli dodatkowo wszystkie jego wierzchołki leżą na obszarze zewnętrznym, graf nazywamy zewnętrznie planarnym. Indeksem krawędziowym grafu G nazywamy najmniejsze k takie, że k-ty iterowany...

Rok 2008
  • Liczba wiązania grafów krawędziowych
    Publikacja

    - Rok 2008

    Liczba wiązania b(G) grafu G jest mocą najmniejszego zbioru krawędzi, których usunięcie z grafu G prowadzi do grafu o liczbie dominowania większej niż gamma(G). Pokazujemy ogólne ograniczenia dla liczby wiązania grafu krawędziowego dowolnego grafu spójnego i grafu pełnego. Ponadto rozważamy liczbę wiązania grafów krawędziowych dla szczególnych przypadków drzew.

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