The Rotor-Router Group of Directed Covers of Graphs
Keywords: finite graphs, directed covers, periodic trees, rotor-router walks, rotor-router group, sandpile group
AbstractA rotor-router walk is a deterministic version of a random walk, in which the walker is routed to each of the neighbouring vertices in some fixed cyclic order. We consider here directed covers of graphs (called also periodic trees) and we study several quantities related to rotor-router walks on directed covers. The quantities under consideration are: order of the rotor-router group, order of the root element in the rotor-router group and the connection with random walks.