Toward a quantum generalization of equilibrium statistical thermodynamics: $\hbar$–$k$ Dynamics

We show that the quantum statistical mechanics (QSM) describing the quantum and thermal properties of objects only has the sense of a particular semiclassical approximation. We propose a more general microdescription than in QSM of objects in a thermal bath with the vacuum explicitly taken into account; we call it $\hbar$–$k$ dynamics. We construct a qualitatively new model of the object environment, namely, a quantum thermal bath. We study its properties including the cases of a "cold" and a "thermal" vacuum. We introduce the stochastic action operator and show its fundamental role in the microdescription. We establish that the corresponding macroparameter, the effective action, plays just as significant a role in the macrodescription. The most important effective macroparameters of equilibrium quantum statistical thermodynamics—internal energy, temperature, and entropy—are expressed in terms of this macroparameter.