REVIEW ARTICLE Equilibration, thermalisation, and the emergence of statistical mechanics in closed quantum systems Christian Gogolin1,2,3 and Jens Eisert1 1Dahlem Center for Complex Quantum Systems, Freie Universitat Berlin, 14195 Berlin, Germany 2ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain 3Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany E-mail:
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[email protected] Abstract. We review selected advances in the theoretical understanding of complex quantum many-body systems with regard to emergent notions of quantum statistical mechanics. We cover topics such as equilibration and thermalisation in pure state statistical mechanics, the eigenstate thermalisation hypothesis, the equivalence of ensembles, non-equilibration dynamics following global and local quenches as well as ramps. We also address initial state independence, absence of thermalisation, and many-body localisation. We elucidate the role played by key concepts for these phenomena, such as Lieb-Robinson bounds, entanglement growth, typicality arguments, quantum maximum entropy principles and the generalised Gibbs ensembles, and quantum (non-)integrability. We put emphasis on rigorous approaches and present the most important results in a unified language. arXiv:1503.07538v5 [quant-ph] 13 Jun 2018 CONTENTS 2 Contents 1 Introduction 3 2 Preliminaries and notation 7 3 Equilibration 16 3.1 Notionsofequilibration. .. 17 3.2 Equilibrationonaverage . 18 3.3 Equilibration during intervals . .... 24 3.4 Othernotionsofequilibration . ... 25 3.5 Lieb-Robinsonbounds ............................ 26 3.6 Time scales for equilibration on average . ...... 28 3.7 Fidelitydecay................................. 33 4 Investigations of equilibration for specific models 33 4.1 Globalquenches................................ 34 4.2 Localandgeometricquenches .