Scaling Down the Laws of Thermodynamics

By Christopher Jarzynski

Department of Chemistry and Biochemistry, University of Maryland, College Park, MD

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Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems often exhibit “thermodynamic-like” behavior – biomolecular motors convert chemical fuel into mechanical work, and individual polymer molecules exhibit hysteresis and dissipation when stretched and contracted. To what extent can the laws of thermodynamics be “scaled down” to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will review recent progress toward answering these questions, focusing in particular on the second law of thermodynamics.

The second law is traditionally stated in terms of inequalities. For microscopic systems these inequalities can be replaced by stronger equalities, known as fluctuation relations, which relate equilibrium properties to far-from-equilibrium fluctuations. The discovery and experimental validation of these relations have stimulated interest in the feedback control of small systems, the closely related Maxwell demon paradox, and the interpretation of the thermodynamic arrow of time. These developments have led to new tools for the analysis of non-equilibrium experiments and simulations, and they have refined our understanding of irreversibility and the second law in nanoscale systems.


Christopher Jarzynski Christopher Jarzynski received his A.B. (with high honors) in 1987 from Princeton University and his Ph.D. in 1994 from University of California, Berkeley. His research focuses on statistical mechanics and thermodynamics at the molecular level, with a particular focus on the foundations of nonequilibrium thermodynamics. His research group has worked on topics that include the application of statistical mechanics to problems of biophysical interest; the analysis of artificial molecular machines; the development of efficient numerical schemes for estimating thermodynamic properties of complex systemsl; the relationship between thermodynamics and information processing; quantum and classical shortcuts to adiabaticity; and quantum thermodynamics.

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  • Christopher Jarzynski (2018), "Scaling Down the Laws of Thermodynamics,"

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