The r-domination search game on graphs is a game-theoretical approach to several graph and hypergraph parameters including treewidth and hypertree width. The task is to identify the minimum number of cops sufficient to catch the visible and fast robber. In r-domination search, the robber is being arrested if he resides inside a ball of radius r around some cop. In this setting, the power of the cops does not depend only on how many they are but also on the local topology of the graph around them. This is the main reason why the approximation complexity of the r-domination search
Fedor V. Fomin, Petr A. Golovach, Dimitrios M. Thi