A broadcast is a function f that assigns an integer value to each vertex of a graph such that, for each v ∈ V , f (v) ≤ e (v), where e(v) is the eccentricity of v. The broadcast number of a graph is the minimum value of ∑ f(v) among all broadcasts f with the property that for each vertex u ∈ V, there exists some v ∈ V with f(v) > 0 such that d(υ,v) ≤ f(v). We present a new upper bound for the broadcast number of a graph in terms of its irredundance number and a new dual property of the broadcast number called the multipacking number of a graph. / Graduate

Suppose there is a transmitter located at each vertex of a graph G. A k-limited broadcast on G is an assignment of the integers 0,1,...,k to the vertices of G. The integer assigned to the vertex x represents the strength of the broadcast from x, where strength 0 means the transmitter at x is not broadcasting. A broadcast of positive strength s from x is heard by all vertices at distance at most s from x. A k-limited broadcast is called dominating if every vertex assigned 0 is within distance d of a vertex whose transmitter is broadcasting with strength at least d. The k-limited broadcast domination number of G is the minimum possible value of the sum of the strengths of the broadcasts in a k-limited dominating broadcast of G. We establish upper and lower bounds for the 2-limited broadcast domination number of various grid graphs, in particular the Cartesian products of two paths, a path and a cycle, and two cycles. The upper bounds are derived by explicit broadcast constructions for these graphs. The lower bounds are obtained via linear programming duality by finding lower bounds for the fractional 2-limited multipacking number of these graphs. Finally, we present an algorithm to improve the lower bound for the 2-limited broadcast domination number of special sub-families of grids. We conclude this thesis with suggested open problems in broadcast domination and multipackings. / Graduate

A broadcast is a function $f:V \rightarrow { 0,...,diam(G)}$ that assigns an integer value to each vertex such that, for each $v\in V$, $f(v)\leq e(v)$, the eccentricity of $v$. The broadcast number of a graph is the minimum value of $\sum_{v\in V}f(v)$ among all broadcasts $f$ for which each vertex of the graph is within distance $f(v)$ from some vertex $v$ having $f(v)\geq1$. This number is bounded above by the radius of the graph, as well as by its domination number. Graphs for which the broadcast number is equal to the radius are called radial. We prove a new upper bound on the broadcast number of a graph and motivate the study of radial trees by proving a relationship between the broadcast number of a graph and those of its spanning subtrees. We describe some classes of radial trees and then provide a characterization of radial trees, as well as a geometric interpretation of our characterization.