Abstract
In many real-world situations, there are constraints on the ways in which a physical system can be manipulated. We investigate the entropy production (EP) and extractable work involved in bringing a system from some initial distribution to some final distribution , given that the set of master equations available to the driving protocol obeys some constraints. We first derive general bounds on EP and extractable work, as well as a decomposition of the nonequilibrium free energy into an “accessible free energy” (which can be extracted as work, given a set of constraints) and an “inaccessible free energy” (which must be dissipated as EP). In a similar vein, we consider the thermodynamics of information in the presence of constraints and decompose the information acquired in a measurement into “accessible” and “inaccessible” components. This decomposition allows us to consider the thermodynamic efficiency of different measurements of the same system, given a set of constraints. We use our framework to analyze protocols subject to symmetry, modularity, and coarse-grained constraints and consider various examples including the Szilard box, the 2D Ising model, and a multiparticle flashing ratchet.
- Received 21 November 2020
- Revised 6 July 2021
- Accepted 9 August 2021
DOI:https://doi.org/10.1103/PhysRevX.11.041024
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
One of the central goals of thermodynamics is to understand how much work can be extracted by driving a physical system between two thermodynamic states. A well-known result says that the maximum amount of extractable work is equal to the drop of free energy between the initial and final states. This bound follows from the second law of thermodynamics, and therefore is a fundamental limit that holds for all physical processes. In general, however, achieving this maximum work bound is possible only under highly idealized conditions. Here, we investigate thermodynamic bounds that apply in nonidealized conditions, of the sort found in the real world, given constraints on how one can manipulate a physical system.
We first develop a general framework that shows how such constraints can be translated to limits on work and entropy production that are stronger than those imposed by the second law. Our framework also quantifies how much work can be extracted from a system using different measurements, in the presence of such constraints. We focus on three general kinds of constraints—symmetry, modularity, and coarse-grained control—which we use to study various canonical systems in statistical physics, such as the Szilard box and the 2D Ising model.
We expect our approach to lead to a better understanding of the thermodynamic efficiency of various real-world systems, ranging from biomolecular machines to recently developed “information engines.”
