How well can the maximum size of an independent set, or the minimum size of a dominating set of a graph in which all degrees are at most d be approximated by a randomized constant time algorithm ? Motivated by results and questions of Nguyen and Onak, and of Parnas, Ron and Trevisan, we show that the best approximation ratio that can be achieved for the first question (independence number) is b...

Let S be the set of minimal dominating sets of graph G and U, W ⊂ S with U ⋃ W = S and U ⋂ W = ∅. A Smarandachely mediate-(U,W ) dominating graph D m(G) of a graph G is a graph with V (D m(G)) = V ′ = V ⋃ U and two vertices u, v ∈ V ′ are adjacent if they are not adjacent in G or v = D is a minimal dominating set containing u. particularly, if U = S and W = ∅, i.e., a Smarandachely mediate-(S, ...

Assume that D is a digraph without cyclic triangles and its vertices are partitioned into classes A1, . . . , At of independent vertices. A set U = ∪i∈SAi is called a dominating set of size |S| if for any vertex v ∈ ∪i/ ∈SAi there is a w ∈ U such that (w, v) ∈ E(D). Let β(D) be the cardinality of the largest independent set of D whose vertices are from different partite classes of D. Our main r...

While efficient algorithms for finding minimal distance-k dominating sets exist, finding minimum such sets is NP-hard even for bipartite graphs. This paper presents a distributed algorithm to determine a minimum (connected) distance-k dominating set and a maximum distance-2k independent set of a tree T . It terminates in O(height(T )) rounds and uses O(log k) space. To the best of our knowledge...

A subset S of vertices in a graph G is a global total dominating set, or just GTDS, if S is a total dominating set of both G and G. The global total domination number γgt(G) of G is the minimum cardinality of a GTDS of G. In this paper, we show that the decision problem for γgt(G) is NP-complete, and then characterize graphs G of order n with γgt(G) = n− 1.

A set S of vertices in a graph G is a total dominating set of G if every vertex of G is adjacent to some vertex in S. The minimum cardinality of a total dominating set of G is the total domination number of G. Let G be a connected graph of order n with minimum degree at least two and with maximum degree at least three. We define a vertex as large if it has degree more than 2 and we let L be the...

For a positive integer k, a set of vertices S in a graph G is said to be a k-dominating set if each vertex x in V (G) − S has at least k neighbors in S. The cardinality of a smallest k-dominating set of G is called the k-domination number of G and is denoted by γk(G). The independence number of a graph G is denoted by α(G). In [Australas. J. Combin. 40 (2008), 265–268], Fujisawa, Hansberg, Kubo...

For a graphical property P and a graph G, we say that a subset S of the vertices of G is a P-set if the subgraph induced by S has the property P. Then the P-domination number of G is the minimum cardinality of a dominating P-set and the P-independence number the maximum cardinality of a P-set. We show that several properties of domination, independent domination and acyclic domination hold for ...

A locating-total dominating set (LTDS) S of a graph G is a total dominating set S of G such that for every two vertices u and v in V(G) − S, N(u)∩S ≠ N(v)∩S. The locating-total domination number ( ) l t G  is the minimum cardinality of a LTDS of G. A LTDS of cardinality ( ) l t G  we call a ( ) l t G  -set. In this paper, we determine the locating-total domination number for the special clas...

For an integer k ≥ 1 and a graph G = (V,E), a set S of V is k-independent if ∆(S) < k and k-dominating if every vertex in V \S has at least k neighbors in S. The k-independence number βk(G) is the maximum cardinality of a k-independent set and the k-dominating number is the minimum cardinality of a k-dominating set of G. Since every kindependent set is (k + 1)-independent and every (k + 1)-domi...