Basic properties for sand automata
  We prove several results about the relations between injectivity and surjectivity for sand automata. Moreover, we begin the exploration of the dynamical behavior of sand automata proving that the property of nilpotency is undecidable. We believe that the proof technique used for this last result might reveal useful for many other results in this context. 
Julien Cervelle (IGM), Enrico Formenti (I3S), Benoit Masson (I3S)