Eternal paired domination in graphs

Eternal dominationof a graph requires the vertices of the graph to be protected, against infinitely long sequences of attacks, by guards located at vertices (at most one guard at each vertex), with the requirement that the configuration of guards induces a dominating set at all times. Two models of the problem, one in which only one guard moves at a time and one in which more than one guard may move simultaneously are studied in the literature. In this paper, we study the model in which more than one guard move simultaneously and where the configuration of guards induces a paired dominating set at all times.