Equilibrium reduced-density operator for nanoscopic systems
1 Quantum Physics Division, Faculty of Physics A. Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
Physica A, 305, 497-520 (2002)
Equilibrium reduced-density operators for subsystems of the Universe are derived from the generalised Schrödinger variational principle, additionally assuming that the values of von Neumann entropy for the subsystems are fixed and higher than zero. The obtained reduced-density operator may be useful for description of the thermodynamical properties of a nanoscopic system, ultrathin films and similar systems.