Efficient (t, r) broadcast dominating sets of the triangular lattice

Blessing, Insko, Johnson and Mauretour gave a generalization of the domination number of a graph G called the (t, r) broadcast domination number which depends on the positive integer parameters t and r. In this setting, a v is an element of V is a broadcast vertex of transmission strength t if it transmits a signal of strength t - d(u, v) to every vertex u is an element of V with d(u, v) < t. Given a set of broadcast vertices S subset of V, the reception at vertex u is the sum of the transmissions from the broadcast vertices in S. The set S subset of V is called a (t, r) broadcast dominating set if every vertex u E V has a reception strength r(u) >= r and for a finite graph G the cardinality of a smallest broadcast dominating set is called the (t, r) broadcast domination number of G. In this paper, we consider the infinite triangular grid graph and define efficient (t, r) broadcast dominating sets as those broadcasts that minimize signal waste. Our main result constructs efficient (t, r) broadcasts on the infinite triangular grid graph for all t >= r >= 1. Using these broadcasts, we then provide upper bounds for the (t, r) broadcast domination numbers for triangular matchstick graphs when (t, r) is an element of {(2, 1), (3, 1), (3, 2), (4, 1), (4, 2), (4, 3), (t, t)}. (C) 2019 Elsevier B.V. All rights reserved.