Quantum thermodynamics

the long version

This tutorial essay views thermodynamics as an incomplete description of quantum systems with many degrees of freedom.The main goal is to show that the approach to equilibrium with equilibrium characterized by maximum ignorance about the open system of interest - does neither require that many particles nor is the precise way of partitioning relevant for the solient features of equilibrium and equilibration. Moreover it is indeed quantum effects that are at work in bringing about universal thermodynamic behaviour of modest size open systems. Von Neumann`s concept of entropy thus appears as much more widely useful than sometimes feared, way beyond truely macrosopic systems in equilibrium.