Not All Fluctuations are Created Equal:
Spontaneous Variations in Thermodynamic Function

J. P. Crutchfield and C. Aghamohammadi

Complexity Sciences Center
Physics and Mathematics Departments
University of California at Davis
Davis, CA 95616


Almost all processes—highly correlated, weakly correlated, or correlated not at all—exhibit statistical fluctuations. Often physical laws, such as the Second Law of Thermodynamics, address only typical realizations—as highlighted by Shannon's asymptotic equipartition property and as entailed by taking the thermodynamic limit of an infinite number of degrees of freedom. Indeed, our interpretations of the functioning of macroscopic thermodynamic cycles are so focused. Using a recently derived Second Law for information processing, we show that different subsets of fluctuations lead to distinct thermodynamic functioning in Maxwellian Demons. For example, while typical realizations may operate as an engine—converting thermal fluctuations to useful work—even “nearby” fluctuations (nontypical, but probable realizations) behave differently, as Landauer erasers—converting available stored energy to dissipate stored information. One concludes that ascribing a single, unique functional modality to a thermodynamic system, especially one on the nanoscale, is at best misleading, likely masking an array of simultaneous, parallel thermodynamic transformations. This alters how we conceive of cellular processes, engineering design, and evolutionary adaptation.

J. P. Crutchfield and C. Aghamohammadi, “Not All Fluctuations are Created Equal: Spontaneous Variations in Thermodynamic Function”, (2016) submitted.
[pdf] 771 KB
Santa Fe Institute Working Paper 16-09-018. [cond-mat.stat-mech].