National Science Foundation (NSF) (DMS-1516866); Office of Naval Research (ONR) (N00014-151-2333); Einstein Stiftung/Foundation - Berlin, Einstein Visiting Fellow Program (to E.S.T.); Ecole Polytechnique Foundation for its partial financial support through the 2017-2018 `Gaspard Monge Visiting Professor' Program (to E.S.T.).