Fluctuation theorems for autonomous work

Abstract

Classical fluctuation theorems for work have been obtained theoretically, and verified experimentally, within a non-autonomous framework in which work is performed on a system of interest, $\mathcal{S}$, by the external manipulation of a work parameter, such as a piston's position. Here we obtain fluctuation theorems within an autonomous framework in which $\mathcal{S}$ exchanges energy with a reversible work source, $\mathcal{R}$. The two subsystems, $\mathcal{R}$ and $\mathcal{S}$, interact with one another as they evolve under Hamiltonian or stochastic dynamics, without external intervention. In this setting, we must account for the back-action of $\mathcal{S}$ on $\mathcal{R}$, which is absent in the non-autonomous setting. We obtain autonomous versions of standard fluctuation theorems for work and entropy production. In each case, we argue, the autonomous fluctuation theorem reduces to its non-autonomous counterpart when $\mathcal{R}$'s inertia becomes infinitely large.

13 pages, 2 figures. Published with Open Access on Dec. 12, 2025, in Proceedings of the National Academy of Sciences (USA). This version contains the published article together with the published Supporting Information