A broadcast on a graph G=(V,E) is a function f : V → {0, ..., diam(G)} that assigns an integer value to each vertex such that, for each v ∈ V , f (v) ≤ e(v), the eccentricity of v. The broadcast number of a graph is the minimum value of Σv∈V f (v) among all broadcasts f with the property that for each vertex x of V, f (v) ≥ d(x, v) for some vertex v having positive f (v). This number is bounded above by both the radius of the graph and its domination number. Graphs for which the broadcast number is equal to the domination number are called 1-cap graphs. We investigate and characterize a class of 1-cap trees. / Graduate

In this thesis we will be working with dominating and interpolating sequences. We worked with a geometric approach and used pseudohyperbolic translated to the Euclidean disc in order to show that a sequence within a certain radius of a dominating sequence is dominating as well.

A set S of vertices of a graph G is a dominating set if every vertex not in S is adjacent to a vertex of S and is a total dominating set if every vertex of G is adjacent to a vertex of S. The cardinality of a minimum dominating (total dominating) set of G is called the domination (total domination) number. A set that does not dominate (totally dominate) G is called a non-dominating (non-total dominating) set of G. A partition of the vertices of G into non-dominating (non-total dominating) sets is a non-dominating (non-total dominating) set partition. We show that the minimum number of sets in a non-dominating set partition of a graph G equals the total domination number of its complement Ḡ and the minimum number of sets in a non-total dominating set partition of G equals the domination number of Ḡ. This perspective yields new upper bounds on the domination and total domination numbers. We motivate the study of these concepts with a social network application.

A set S of vertices in a graph G = (V,E) is a total dominating set of G if every vertex of V is adjacent to a vertex in S. We consider total dominating sets of minimum cardinality which have the additional property that distinct vertices of V are totally dominated by distinct subsets of the total dominating set.

Given a graph with domination number γ, we find bounds on the maximum number of minimum dominating sets. First, for γ≥3, we obtain lower bounds on the number of γ-sets that do not dominate a graph on n vertices. Then, we show that γ-fold lexicographic product of the complete graph on n1/γ vertices has domination number γ and γn-O(nγ-γ/1) dominating sets of size γ. Finally, we see that a certain random graph has, with high probability, (i) domination number γ; and (ii) all but o(nγ) of its γ-sets being dominating.

A coalition in a graph G =(V, E) consists of two disjoint sets of vertices V1 and V2, neither of which is a dominating set of G but whose union V1 ∪ V2 is a dominating set of G.A coalition partition in a graph G of order n = |V| is a vertex partition π= {V1, V2,⋯, Vk} of V such that every set Vi either is a dominating set consisting of a single vertex of degree n - 1, or is not a dominating set but forms a coalition with another set Vj which is not a dominating set. Associated with every coalition partition πof a graph G is a graph called the coalition graph of G with respect to π, denoted CG(G, π), the vertices of which correspond one-to-one with the sets V1, V2,⋯, Vk of πand two vertices are adjacent in CG(G, π) if and only if their corresponding sets in πform a coalition. In this paper we study coalition graphs, focusing on the coalition graphs of paths, cycles, and trees. We show that there are only finitely many coalition graphs of paths and finitely many coalition graphs of cycles and we identify precisely what they are. On the other hand, we show that there are infinitely many coalition graphs of trees and characterize this family of graphs.

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A set of vertices in a graph G is a global dominating set of G if it dominates both G and its complement G. The minimum cardinality of a global dominating set of G is the global domination number of G. We explore the effects of graph modifications (edge removal, vertex removal, and edge addition) on the global domination number. In particular, for each graph modification, we study the global domination stable trees, that is, the trees whose global domination number remains the same upon the modification. We characterize these stable trees having small global domination numbers.

A set of vertices in a graph G is a global dominating set of G if it dominates both G and its complement G. The minimum cardinality of a global dominating set of G is the global domination number of G. We explore the effects of graph modifications (edge removal, vertex removal, and edge addition) on the global domination number. In particular, for each graph modification, we study the global domination stable trees, that is, the trees whose global domination number remains the same upon the modification. We characterize these stable trees having small global domination numbers.

Consider a configuration of pebbles distributed on the vertices of a connected graph of order n. A pebbling step consists of removing two pebbles from a given vertex and placing one pebble on an adjacent vertex. A distribution of pebbles on a graph is called solvable if it is possible to place a pebble on any given vertex using a sequence of pebbling steps. The pebbling number of a graph, denoted f (G), is the minimal number of pebbles such that every configuration of f (G) pebbles on G is solvable. We derive several general upper bounds on the pebbling number, improving previous results.