“…This connection is in fact rather natural: long time after a quench, the reduced density matrix of a subsystem is commonly accepted to be the one of the mixed state compatible with all the local integrals of motion, i.e. a generalized Gibbs ensemble (GGE) for an integrable system [24,25,26,27,28,29,30,31,32,33,34,35,36,37,38] and a thermal ensemble for a generic system [39,40,41,42,43,44,45,46], see also Ref. [47] for a review.…”