Throttling for Zero Forcing and Variants

Abstract

Zero forcing is a process on a graph in which the goal is to force all vertices to become blue by applying a color change rule. Throttling minimizes the sum of the number of vertices that are initially blue and the number of time steps needed to color every vertex. We introduce a new universal definition of throttling for variants of zero forcing and the study of throttling for the minor monotone floor of zero forcing. We introduce the technique of using a zero forcing process to extend a given graph. For standard zero forcing and its floor, we use these extensions to characterize graphs with throttling number $\leq t$ as certain minors of Cartesian products of complete graphs and paths. We apply these characterizations to determine graphs with extreme throttling numbers.