Counterfactual thermodynamics: Extracting work from a lack of macroscopic change

Abstract

A sudden change in the macroscopic parameters of a system will cause it to depart from equilibrium. In this paper we study how a lack of change can also inform of such a departure, and allow for work extraction. Potential events that are unrealized can provide information pertaining the microstates of the system, essentially playing the role of a passive Maxwell demon, thereby allowing one to infer details about the microstate probability distribution. Here, we first qualitatively argue that this effect is present and consequential in almost every physical system, but is ignored in the standard formulation of equilibrium statistical mechanics. Then, as a case study, we quantitatively investigate the local and global thermodynamic properties of an ideal gas placed in a fragile container that nevertheless, does not burst. This non-event indicates a departure from equilibrium and allows work extraction from the system. It also leads to corrections to the heat capacity of the gas.