Universal theory of efficiency fluctuations

TL;DR

This paper derives universal features of efficiency fluctuations in thermal and isothermal engines using fluctuation theorems, revealing symmetry properties and the probability of reversible efficiency under various driving conditions.

Contribution

It introduces a universal theoretical framework for understanding efficiency fluctuations in steady and periodically driven thermal machines, extending fluctuation theorem applications.

Findings

Reversible efficiency probability equals that under time-reversed driving.

Symmetric driving makes reversible efficiency the least probable.

Universal features hold for engines operating far from equilibrium.

Abstract

Using the fluctuation theorem supplemented with geometric arguments, we derive universal features of the (long-time) efficiency fluctuations for thermal and isothermal machines operating under steady or periodic driving, close or far from equilibrium. In particular, the long-time probability for observing a reversible efficiency in a given engine is identical to that for the same engine working under the time-reversed driving. When the driving is symmetric, this reversible efficiency becomes the least probable.