“…Among the main results, one may cite the existence of a well-defined 'rotation number' for any minimizing configuration, the 'total ordering property' of the set of minimizing configurations with a fixed rotation number, and the existence of a unique 'hull function' up to a phase shift which parametrizes all minimizing configurations with a fixed rotation number. These main results have been obtained by several authors, first by Aubry and Le Daeron [3], Aubry et al [4], Griffiths et al [37], independently by Mather [48,51], more recently by Gomes and Oberman, Rorro and Falcone [20,33,34,53], Baesens and MacKay [6], and in a similar context of ergodic optimization by Bousch, Brémont, Jenkinson and Morris, Bressaud and Quas, Leplaideur [9,10,12,13,39,40,42]. The minimizing configurations previously described correspond to equilibrium fixed points of the steady-state Frenkel-Kontorova equation.…”