  We develop a general formulation of quantum statistical mechanics in terms of
probability currents that satisfy continuity equations in the multi-particle
position space, for closed and open systems with a fixed number of particles.
The continuity equation for any closed or open system suggests a natural
Bohmian interpretation in terms of microscopic particle trajectories, that make
the same measurable predictions as standard quantum theory. The microscopic
trajectories are not directly observable, but provide a general, simple and
intuitive microscopic interpretation of macroscopic phenomena in quantum
statistical mechanics. In particular, we discuss how various notions of
entropy, proper and improper mixtures, and thermodynamics are understood from
the Bohmian perspective.
