Non-monotonic skewness of currents in non-equilibrium steady states

Abstract

Measurements of any property of a microscopic system are bound to show significant deviations from the average, due to thermal fluctuations. For time-integrated observables such as heat, work or entropy production in a steady state, it is in fact known that there will be long stretches of fluctuations both above as well as below the average, occurring equally likely at large times. In this paper we show that for any finite-time measurement in a non-equilibrium steady state -rather counter-intuitively -fluctuations below the average are more probable; there is even an optimal time for time-integrated current fluctuations to most likely lie below the average. We demonstrate that these effects are a consequence of the non-monotonic skewness of current fluctuations in nonequilibrium stationary states. We also provide evidence that our findings are easily observable in experiments.