Nonequilibrium Entropy and the Second Law in Quantum Many-Body Systems

This is an introductory talk about the second law of thermodynamics and the associated problem of finding a meaningful notion of (thermodynamic) entropy; (mostly) viewed from the perspective of quantum many-body systems, ultracold atoms and open quantum systems.

The talk starts by reviewing the second law and entropy concept from a phenomenological and historical perspective. Afterwards, three different candidates to define thermodynamic entropy are discussed: the familiar von Neumann and Boltzmann entropies and the (not so familiar) observational entropy (albeit the latter was explicitly proposed by von Neumann as the correct entropy concept in statistical mechanics). Based on this last entropy candidate, the talk finishes by explaining how the second law can be derived and quantified in isolated quantum systems.