“…Only for few infinite families of graphs, the structure of the respective sandpile groups has been (partly) determined, including complete graphs [39], complete multipartite graphs [29], cycles (equivalent to domains of Z 1 ) [39], thick cycles [1] (see also [26]), wheels [12,43], modified wheels [45], wired regular trees [38], thick trees [19], polygon flowers [17], nearly complete graphs [43], threshold graphs [43], Möbius ladders [18,24], prism graphs/graphs D n of the dihedral group [23,24], and n-cubes [6,2]. While this list is certainly not complete, the decomposition of the sandpile group on domains of Z 2 , for which the sandpile model was originally defined [7], is-to our knowledge-yet unknown.…”