The beat of a current

Pedro E. Harunari, Alberto Garilli, Matteo Polettini

Published 2022-05-10Version 1

The fluctuation relation, milestone of thermodynamics based on Markov processes, is only established when a set of fundamental currents can be measured and all transitions are reversible. Here we prove that it also holds for systems with hidden transitions (possibly irreversible) if observations are carried "at their own beat", that is, by stopping the experiment after a given number of visible transitions rather than after the elapse of an external clock time. This suggests that thermodynamics may be best described by Markov processes in the space of transitions, rather than states.