Seminars & Colloquia Calendar

ABSTRACT: It is customary to use the canonical ensemble to represent a system that is in equilibrium with a thermal reservoir. Although familiar macroscopic relations between internal energy, entropy, free energy, heat and work are easily derived from the canonical ensemble, this ensemble does not accurately describe a nanoscale system that is strongly coupled to its surroundings, such as a biomolecule in aqueous solution. I will discuss a modified thermodynamic framework that describes a classical system of arbitrary size that is strongly coupled to its thermal environment.  Within this framework, key thermodynamic quantities are defined microscopically and are shown to obey thermodynamic relations including both the first and second law, as well as nonequilibrium fluctuation theorems. These quantities scale up to their macroscopic values when the system of interest is large. Thus a unifying framework is developed, which encompasses nanoscale, stochastic thermodynamics at one end, and traditional macroscopic thermodynamics at the other. A central element in this approach is a thermodynamic definition of the volume of the system of interest, which converges to the usual geometric definition when the system is large.